GT200 with Malossi 218, 4v, cam, lv4road. No change?
Post Reply    Forum -> General Discussion 12345Next
Author Message
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Fri Dec 08, 2017 10:33 pm quote
I posted this originally on another thread, but the question requires a new topic I think.

Okay, so with the Malossi 4v head, 218 cyl and cam the performance is almost the same as it was stock. Thinking it might be a variator problem I tried WOT and achieved very nearly the same indicated top speed 120kmh. The bike (GT200) already had a LV 4road exhaust and Malossi filter.

When I picked up the bike and took it for a mid paced breaking in ride it felt lean (as it should have) with a bit of back popping on deceleration and a few flat spots. When I had a few kms on it I tried WOT and found it went better at 3/4. I upped the main jet to 100 (95 original on the Walbro carb) which sort of fixed WOT, but nothing slightly interesting in the mid range. I raised the needle by a notch and that helped fill it out, but the result is VERY similar before and after these mods. I haven't put a tach on it, though I've got one comming, but WOT at top speed should have it in the 8000rpm+ range which is enough for the setup to be doing it's thing.

Any ideas?
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Fri Dec 08, 2017 10:59 pm quote
Something has changed though as it is much louder. Extended cam and bigger valves would explain that, but where is the horsepower?
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sat Dec 09, 2017 1:20 am quote
One other thing, at about 1/3 throttle the performance is better, it's just that it doesn't get much better between that and full, though it does get louder. 1/2 throttle is slightly better, after that it's close to stock.
Hooked
"MY WIFES" 2010 GTS FASTER & BETTER ENGINEERED THAN YOURS!!
Joined: 23 Jan 2017
Posts: 488
Location: STAYOFFVILLE
Sat Dec 09, 2017 7:01 am quote
is the airbox modified to accommodate the additional airflow?
I read you had an aftermarket filter but on my gts & sc... the intake runner is tiny and some minor trimming made a significant difference.

And does the carb slide modulate the same as the throttle cable? Like when youre WFO is the slide all the way up?
Ossessionato
Joined: 22 Oct 2011
Posts: 3848
Location: Tega Cay, SC
Sat Dec 09, 2017 8:23 am quote
The top speed won't change unless you change out the gearing. But with this setup, you should have gotten to top speed quicker. Somethings amiss.
Ossessionato
09 190s taormina
Joined: 08 Apr 2010
Posts: 2082
Location: Googleville
Sat Dec 09, 2017 10:52 am quote
Lose or gut the airbox and get a slide carb. From my experience carb swap freed up most power.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sat Dec 09, 2017 3:40 pm quote
Thanks for the replies. I can experiment with the airbox pretty easily so I'll do that first. I'll just remove it for a minute and it should be obvious if it makes a difference.

I'm not sure how to tell what the slide is doing without sticking my head under the seat at WOT. I might not be doing that! My carb is a Walbro 33mm the cable doesn't connect to the slide, it's operated by vacuum. The cable does the butterfly.

I'm not sure why some people think top speed isn't directly affected by horsepower. Unless the engine was already running on the rev limiter it obviously is. When you redesign an engine to run at 10000rpm with 22hp at the wheel it is going to effect top speed when the old one did 8800rpm with 16.5hp. It's got nothing to do with gearing. Sorry for the rant but I've read so much of this while researching on MV.
Ossessionato
LXV 150 Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 2780
Location: Bangkok
Sat Dec 09, 2017 5:33 pm quote
Mike will be along soon?

My thinking is that by changing the cam you have moved the power further up the rev range but have not changed the variator to allow the engine to work in the new range.
Hooked
"MY WIFES" 2010 GTS FASTER & BETTER ENGINEERED THAN YOURS!!
Joined: 23 Jan 2017
Posts: 488
Location: STAYOFFVILLE
Sat Dec 09, 2017 6:07 pm quote
Caketin wrote:
Thanks for the replies. I can experiment with the airbox pretty easily so I'll do that first. I'll just remove it for a minute and it should be obvious if it makes a difference.

I'm not sure how to tell what the slide is doing without sticking my head under the seat at WOT. I might not be doing that! My carb is a Walbro 33mm the cable doesn't connect to the slide, it's operated by vacuum. The cable does the butterfly.

I'm not sure why some people think top speed isn't directly affected by horsepower. Unless the engine was already running on the rev limiter it obviously is. When you redesign an engine to run at 10000rpm with 22hp at the wheel it is going to effect top speed when the old one did 8800rpm with 16.5hp. It's got nothing to do with gearing. Sorry for the rant but I've read so much of this while researching on MV.
you might have to rent some dyno time to see whats going on at WOT. At least so you can eliminate some things.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sat Dec 09, 2017 8:23 pm quote
Not much in the way of dynos here in Western Australia. I totally agree with the comment regarding the cam, but that is why I took it to full speed. The reasoning being the variator seems to run out around 110kmh then the revs start to climb. The original peak hp is around 8-8500rpm so I reasoned Piaggio would have had the variator locking in at around 8000 and by 120 maybe 8800. Using the Malossi dyno chart as a guide, this is well into the power range of the new cam and about 30% more hp and torque than standard at that speed, so I really would have expected to push on to at least 130-135 where the power start to ebb.

I have a tacho coming so when that arrives I'll fit it up and see what's going on. If it's only doing 7k rpm that would explain most of the problem. It's still the original variator and rollers, but in the past I've noticed worn variators, belt and rollers tend to lift the rpm. I must admit the revs don't seem to come up as early as they did when it was new. The variator used to run out at about 100kmh and the revs lifted from there.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sat Dec 09, 2017 8:42 pm quote
One more question, for those with after market variators and a tacho, say you have the variator set to give 8500 at WOT, how many rpm are you doing when only light throttle is applied? I watched the SIP instrument video where they had the panel fitted to a GTS300. At gentle acceleration is was doing about 5500, but at WOT it was about 7500rpm. If this is true then even with a variator set to optimum hp around 8500 for my GT, it wouldn't be ringing it's guts out when just tootling about, which is the only reason I haven't done anything with the variator yet. I wouldn't want to be rolling along admiring the scenery with the engine screaming at 8500, I'd sound and feel like a twat, I am 52.

I'm also curious to know if this band of rpm at light and heavy throttle is the same on the various after market variators as I understand they use different ramp angles. In stock form and mid throttle mine climbs rpm between 40 and 80kmh, not a lot, perhaps 700. At WOT it actually drops a little after about 60kmh. Power ebbs quickly after the drop which does suggest it maybe dropping out of the cam's band.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sat Dec 09, 2017 9:27 pm quote
Back again after a bodgy rig up made by cable tying one of the leads of my multimeter to the spark plug lead and setting it on Hertz. Not very accurate, but any reading is better than a guess.

It's all over the place. If I go from a standing start at WOT it sometimes exceeds 8000rpm, but dives to under 7k when it hits around 60kmh. rolling from a start then opening it up it sometimes never gets over 7k. On another run from rest at WOT it held onto the 8k to 100kmh. I was on a small road so given I was watching a multimeter swinging from one of the mirrors by it's clamp I elected not to go any faster. That time the revs didn't sound as if they'd dropped either and acceleration was decidedly better. Around a corner I opened it up from 60kmh and it barely hit 7k again, once it bogged in at 6500.

It's not really lightening the weights that will fix that, I'm going to need another variator. I'll wait until I've got a proper tach before I fiddle much more though. I'm now not sure if the variator is still holding the revs down at 120kmh, it never used too, but thinking of belt wear (It's still within limits but not new) it could be laying lower on the driven pulley relative to the drive pulley thus making the overall gearing taller through the range. If wind resistance meets the horse power curve too early I suppose that would limit top end.

Is any of this making sense?
Sponsor
Granturismo 218
Joined: 04 Feb 2013
Posts: 5348
Location: South Carolina
Sat Dec 09, 2017 11:01 pm quote
The cam timing is off by a tooth. They didn't use the mark on the flywheel, they used one on the waterpump. You have to remove the waterpump to see the mark on the flywheel. Take the manual in and show them where the timing mark is.
Also, find out if they trimmed the oil scraper ring to make it fit. If they did, you might as well buy another set and have them do it right when they are in there again, or your next thread will be about how much oil it's using.

Last edited by Motovista on Sat Dec 09, 2017 11:09 pm; edited 1 time in total
Sponsor
Granturismo 218
Joined: 04 Feb 2013
Posts: 5348
Location: South Carolina
Sat Dec 09, 2017 11:05 pm quote
Tierney wrote:
The top speed won't change unless you change out the gearing. .
Not true. It holds about 5 or 6 mph faster with stock gearing.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sat Dec 09, 2017 11:20 pm quote
Valuable Motovista, I wondered myself as I did it in a car once. I didn't want to insult my very experienced Italian Vespa mech as he tried so hard to do everything perfectly, but hasn't had a lot of experience with modern Vespas. ( He did do his apprenticeship with Lamborghini though). Having a tangential question like that though is useful.
Sponsor
Granturismo 218
Joined: 04 Feb 2013
Posts: 5348
Location: South Carolina
Sat Dec 09, 2017 11:36 pm quote
Caketin wrote:
Valuable Motovista, I wondered myself as I did it in a car once. I didn't want to insult my very experienced Italian Vespa mech as he tried so hard to do everything perfectly, but hasn't had a lot of experience with modern Vespas. ( He did do his apprenticeship with Lamborghini though). Having a tangential question like that though is useful.
If he didn't pull the waterpump, you have your answer. Do not let him try to convince you that it's right and spend a couple of months doing workarounds with the carb and variator and whatever else the internet tells you it might be, without actually visually checking the cam timing against the flywheel. The difference between the stock setup and the Malossi setup is like night and day, unless the cam is off a tooth. Then it runs exactly like you are describing. And I know this from personal experience.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sun Dec 10, 2017 12:38 am quote
Got it.

From my experience with this chap (I'm an engineer and can detect bullshit on that topic at 100 paces) I don't think he'll try to cover it up. We've discussed a lot and so far we've been in agreement on even the most controversial of issues. He hasn't pretended to be a hero mechanic and has listened to and followed advice (Rare in my experience). I agree though, that needs to be totally eliminated first. If I have any doubts I'll check myself. I was going to install the kit myself, but I chose a no fuss solution.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sun Dec 10, 2017 1:03 am quote
Without doing a lot of research, what is the easiest way for me to check this?
Veni, Vidi, Posti
LX190
Joined: 12 Oct 2007
Posts: 5738
Location: New Zealand
Sun Dec 10, 2017 1:53 am quote
Caketin wrote:
I was going to install the kit myself, but I chose a no fuss solution.


Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sun Dec 10, 2017 1:58 am quote
Lol. Really this time.
Sponsor
Granturismo 218
Joined: 04 Feb 2013
Posts: 5348
Location: South Carolina
Sun Dec 10, 2017 9:56 am quote
Caketin wrote:
Without doing a lot of research, what is the easiest way for me to check this?
http://www.wotmeworry.org.uk/manuals/Vespa/GT200/GT200Workshop.pdf

Page 146 Shows TDC on the flywheel

What he probably used was the mark on the waterpump on page 68, which puts you one tooth off.

Take the waterpump off, you don't have to drain it to do this, just loosen the bolts, pull it off the flywheel and push it up out of the way so you can see the mark, and then rotate the engine until it's at tdc. A lot easier if you remove the spark plug first. Then check the position of the cam. That's harder, because you can't get a straight view from the side. Use a mirror. or pull the motor if you have to.

The big problem you run into with all the workarounds and other rabbit holes you get sent down is that you can either change something that can't be changed back, like cutting chunks out of your air box, or you do so many things that you have to undo, so it's still not right, after this is right.
Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1947
Location: Not really sure but I think somewhere down South, in the engineering dept at Starfleet's UK HQ
Sun Dec 10, 2017 10:54 am quote
Motovista wrote:
Caketin wrote:
Valuable Motovista, I wondered myself as I did it in a car once. I didn't want to insult my very experienced Italian Vespa mech as he tried so hard to do everything perfectly, but hasn't had a lot of experience with modern Vespas. ( He did do his apprenticeship with Lamborghini though). Having a tangential question like that though is useful.
If he didn't pull the waterpump, you have your answer. Do not let him try to convince you that it's right and spend a couple of months doing workarounds with the carb and variator and whatever else the internet tells you it might be, without actually visually checking the cam timing against the flywheel. The difference between the stock setup and the Malossi setup is like night and day, unless the cam is off a tooth. Then it runs exactly like you are describing. And I know this from personal experience.
Well said boy! This thought was sliding through my brain too! I know you are right...
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sun Dec 10, 2017 5:22 pm quote
I knew about the mark on the flywheel, I just didn't know there was one on the water pump too. It was how to easily get to the cam sprocket to check I was asking. I could probably pressurise the cylinder through the inlet tube and listen at the spark plug hole or visa versa and work it out if I knew the cam timing, which I don't.

Last edited by Caketin on Sun Dec 10, 2017 6:07 pm; edited 1 time in total
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sun Dec 10, 2017 6:07 pm quote
I don't suppose anyone knows when the inlet valve opens? I'd guess it's around 30deg BTDC (crank degrees).
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sun Dec 10, 2017 6:18 pm quote
If it's a whole tooth out I could presume that the duration would be split roughly 1:2 before TDC and after BDC. If it opened at 30deg TDC it should close in the vicinity of 60deg after BDC. The problem here is it's a 37 tooth cam sprocket, roughly 20 crankshaft degrees for a skipped tooth. Some cams would open 10deg BTDC and close 60deg after so without knowing the cam details I wouldn't be confident even with that method.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sun Dec 10, 2017 7:47 pm quote
I think it is ok, I had a chat to Ivo and he tells me they marked both sprockets and the chain and fitted the new one in the standard position. I'm guessing it's the very low rpm that is causing most of the problem. I've played with the carb a bit more and on the few occasion I can coax the variator to let it rev it pulls very well. It also idles smoother than it should with a 20deg retarded or advanced cam.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Sun Dec 10, 2017 9:04 pm quote
Sorry to hog my own thread but I think I've worked out what's going on with the random behaviour of the variator too.

Judging by the rattle at idle the rollers all have flat spots (They might be original, I can't remember changing them). If some rollers are sitting on their flat spots and others aren't they are all going to be in different positions relative to the centre. If all were on a flat the spread would be less at a given rpm, if all on a round it would be more. If it's a mix of the two it could be anything. This might explain why one launch goes to 8k and stays there, the next one struggles at 7k then drops to 6.5.
Sponsor
Granturismo 218
Joined: 04 Feb 2013
Posts: 5348
Location: South Carolina
Sun Dec 10, 2017 10:44 pm quote
Sounds like he convinced you the cam timing is right. Ask him if he cut the scraper ring to make it fit too. My bet is that he did.
Instead of coming up with unique methods of pressurizing the cylinder to check cam timing and non-reality based theories about how variators work that will probably not gain widespread acceptance and definitely won't fix your problem, you might want to take the bike back to the mechanic and have him line up the timing mark on the flywheel and the mark on the cam sprocket so they are both at TDC AT THE SAME TIME. It's really that simple. That's why they put the marks there. Nobody checks it any other way, including the way he did it and the ways you are inventing to do it.

If you're not easily hitting 135 KPH on the flat, the kit's not in right.
Ossessionato
LXV 150 Midnight Blue (Sold)
Joined: 06 Dec 2010
Posts: 2780
Location: Bangkok
Sun Dec 10, 2017 11:32 pm quote
Motovista wrote:
line up the timing mark on the flywheel and the mark on the cam sprocket..... Nobody checks it any other way
That' s the way I would have done it.

BTW Old school or clumsy but for a quick check you can check TDC with a screw driver/ coat hanger down the spark plug hole. If getting to the flywheel is too difficult.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Mon Dec 11, 2017 1:33 am quote
"Sounds like he convinced you the cam timing is right"

Wow, you chaps are really cynical. I'm getting tired of the web.

I'm not a bloody idiot, I've made my living by judging peoples worth for 30 years. I have also managed an engineering company for a similar period of time and if some knob came to me and told me authoritatively that I'd done something wrong without evidence and to pull it apart again at my expense to prove me wrong I would have told him to fuck off, and fuck off while he was doing it.

I was very careful with the work my lads did, I would need something better than a bloke with an attitude problem to start wasting labour to prove it was flawed.

I don't know what land you live in, but in Australia the vast majority of people aim to do the right thing, if they don't their business won't last a year. If they have fucked up, an offer such as I made, to pay for the labour to fix it, would be enough for them to pull it apart and show me it was ok, or if not, fix it and cop the expense themselves. No pressure there.

What Ivo thought I meant is I had hoped he had advanced the cam a tooth for more top end, which he apologised for not realising that's what I wanted.

I think you have mistaken me for a gullible newb. I've spent over $10m on engineered items, most un-contracted or quoted, I'm quite capable of sussing out a scooter mechanic.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Mon Dec 11, 2017 1:38 am quote
And while I'm having a rant, your suggestion to check the timing on the cam was to pull the engine, mine was to pressurise a port. So that's a days worth of work v 15 minutes.

And no, he didn't cut the oil ring, he watched Robbot's video before he started to make sure he wasn't missing anything, as I had suggested. That caused him to check for valve leak, which there was on the inlet, so he re-lapped them.
Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1947
Location: Not really sure but I think somewhere down South, in the engineering dept at Starfleet's UK HQ
Mon Dec 11, 2017 2:27 am quote
Caketin, steady! It's ok to have a bit of a rant, it's an annoying situation. But no one is taking you for a newbie. But you did ask for advice and we don't know your ability. And from what you are saying you don't seem to quite fully understand some of the issues you are describing. We can only go of course by what you are saying, but Motovista is one of the most experienced Vespa engineers on the site and runs a business supplying Vespa parts. There isn't much he doesn't know. I'm and ex-engine design and development engineer and an ex-tech and I can see you are struggling a bit on this. What Motovista is saying makes perfect sense and it wouldn't be the first time I've come across a similar problem caused by this. By all means check your TDC using whatever method you wish but if not done correctly you'll still have an issue if the timing is off. I've found the best way is follow the book. If you don't want to do that then that's fine but you may end up doing lots of trial and error. If the bike came to me for assessment, I'd have the water pump cover off irrespective of what the installing technician had done to cover all bases. It's usually one of the first things to do after checking the obvious. Water pump cover removal takes just minutes, refitting is almost as easy. I don't cut corners when someone is having issues like this. Good luck with all this, it should be a flyer when you've sorted it. Sorry you feel agrieved.

Last edited by Stromrider on Mon Dec 11, 2017 12:21 pm; edited 2 times in total
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Mon Dec 11, 2017 2:31 am quote
Thanks for reply, I understand I sound a bit grumpy, but checking the TDC is easy, I'm not worried about removing the water pump, it's checking the cam relative to that that's difficult.
Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1947
Location: Not really sure but I think somewhere down South, in the engineering dept at Starfleet's UK HQ
Mon Dec 11, 2017 2:38 am quote
Caketin wrote:
Thanks for reply, I understand I sound a bit grumpy, but checking the TDC is easy, I'm not worried about removing the water pump, it's checking the cam relative to that that's difficult.
I think we all understand how you feel, and it's ok to be grumpy! You shouldn't have to drop the engine to check the cam relative to the the lower engine mark. Although it's a bit easier. I use a mirror on a stalky thingy to get a good view. Jacking the bike up also helps to get more of the cylinder and head into view. I do the tappets without undoing the rear shocks and slightly jacking the bike. Admittedly there is a slight knack to learn but it's doable and makes the job quick and easy. So, I'd concentrate on the engine and don't worry about the variator just yet. Your engine should still be punching you to a good speed, higher than you are currently getting. Replace your rollers etc later.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Mon Dec 11, 2017 2:48 am quote
I have been dealing with four stroke engines since I was a kid in the late 70s. Cam timing was a thing then. I only took offense as I was being told I had selected a fool of a mechanic through my naivety. I have met enough hero mechanics to spot one at a distance, and this one isn't one. There is no chance he would start chopping bits off rings without discusng it with me first. Zeroing in on a possible problem then quickly blaming a fool mechanic on the other side of the world is not respectful without some background information. I used to be regularly accused of doing stupid things that I never did when I first started designing for our engineering company, so I'm touchy.

If I did force him to take the engine apart, at my cost, to prove everything was as it should be, who is the winner there? I'm out of pocket and have the only half decent Vespa mechanic in Western Australia doubling his bill in future, as I would.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Mon Dec 11, 2017 2:49 am quote
Thanks Stormrider, I have a crane, so though a little risky, it does let me get underneath!
Molto Verboso
2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 1947
Location: Not really sure but I think somewhere down South, in the engineering dept at Starfleet's UK HQ
Mon Dec 11, 2017 3:26 am quote
Caketin wrote:
I have been dealing with four stroke engines since I was a kid in the late 70s. Cam timing was a thing then. I only took offense as I was being told I had selected a fool of a mechanic through my naivety. I have met enough hero mechanics to spot one at a distance, and this one isn't one. There is no chance he would start chopping bits off rings without discusng it with me first. Zeroing in on a possible problem then quickly blaming a fool mechanic on the other side of the world is not respectful without some background information. I used to be regularly accused of doing stupid things that I never did when I first started designing for our engineering company, so I'm touchy.

If I did force him to take the engine apart, at my cost, to prove everything was as it should be, who is the winner there? I'm out of pocket and have the only half decent Vespa mechanic in Western Australia doubling his bill in future, as I would.
Ah yes! I know what you mean. Motovista would not deliberately be disrespectful, and to be honest, there have been quite a few folks with this very problem and it's nearly always the timing is off, and/or the bottom oil scraper ring has been cut to make it fit in the piston grove. Also, quite often techs say they are used to working on scooters but actually they don't know what they are doing on a Vespa. All quite common! Your symptoms you describe are classic and point to one or more of these things. However, we could be wrong of course. Internet diagnosis is not the best way, we can only all talk about what we think is wrong. You provided quite a bit of helpful information too and I had pretty much reached the same conclusion as Motovista on this during a conversation over dinner. Yes...we actually talk about peoples engine problems over dinner!! Lol. Obviously, the variator is playing a part in your situation but that can be a secondary issue I'm guessing, unless it's totally worn out and the rollers are full of flats everywhere it shouldn't be holding you back that much.
Hooked
GT200
Joined: 12 Nov 2017
Posts: 112
Location: Darlington Western Australia
Mon Dec 11, 2017 3:38 am quote
I agree.

That's why I tried max speed because it should have let the revs climb into the power band, but it didn't.

That is why I also still suspect cam timing, but I can't just front up to a bloke who has never pretended he's n expert on modern Vespas and accuse him of fucking it up without checking myself.

Which bring us back to the start, how can I relatively easily check the cam timing without wasting a day pulling the engine out?

This is why I thought that checking it by putting a protractor on the flywheel and presurising the piston to check the inlet port opening seemed to be an easy solution. What I got back from Motorvista was ridicule for such a naive idea.
Molto Verboso
Joined: 31 May 2009
Posts: 1220
Location: NC, USA
Mon Dec 11, 2017 4:45 am quote
What they said. I have zero four-stroke Vespa experience.

Cylinder pressure as tested with a compression tester might help if you know what it should be with your set up. I've made a LOT of cam selection/timing mistakes in a different life.
Sponsor
Granturismo 218
Joined: 04 Feb 2013
Posts: 5348
Location: South Carolina
Mon Dec 11, 2017 7:28 am quote
Caketin wrote:
I agree.

That's why I tried max speed because it should have let the revs climb into the power band, but it didn't.

That is why I also still suspect cam timing, but I can't just front up to a bloke who has never pretended he's n expert on modern Vespas and accuse him of fucking it up without checking myself.

Which bring us back to the start, how can I relatively easily check the cam timing without wasting a day pulling the engine out?

This is why I thought that checking it by putting a protractor on the flywheel and presurising the piston to check the inlet port opening seemed to be an easy solution. What I got back from Motorvista was ridicule for such a naive idea.
I stated earlier that he would probably try to convince you that the cam timing is correct, and you replied in a later post, "I think it is ok, I had a chat to Ivo and he tells me they marked both sprockets and the chain and fitted the new one in the standard position." No matter how good a mechanic he is, he didn't actually check the cam timing, probably because he's not done one of these engines before.

The very easy way to check cam timing is to use the marks Piaggio placed there for you to do so. One is, as mentioned, on the flywheel. The other is on the sprocket on the cam. I think I even mentioned in an earlier post that it is possible to do this without pulling the engine, by using a mirror. You might also need a flashlight. Here is the way to check it in the privacy of your own garage without further wailing and gnashing of teeth:

First, remove the water pump cover and push to the side so you can see the flywheel and the bottom left corner of the engine case.
Second, remove the valve cover.
Align the arrow on the flywheel cover with the mark on the crankcase. Page 146 of your workbook.
Now, turn to page 179 of your workbook and look at the picture of the timing mark on the camshaft. Compare it to the alignment of the marks in your engine. Use of a mirror and flashlight may help you see it. if yours doesn't match, your cam timing is off. Close doesn't count. It has to be right on the mark.
And that's all there is to it.

Also, if you followed the instructions in any video that told you to do a leakdown test and lap the valves if they weren't seated completely on the new head, you didn't install the kit according to the instructions of the manufacturer.
Cross Egypt Challenge - A 2400km ride throughout Egypt   vespa scooterwest scooter west Motorsport Scooters   Cool Ass scooter seat cover
Post Reply    Forum -> General Discussion 12345Next
[ Time: 0.3062s ][ Queries: 23 (0.0564s) ][ Debug on ]