Modern Vespa

Now getting happy with my 221 again. Seems to be going quite nicely at the moment. In the never ending search for more. It was time to lag the exhaust and see what happens.

The idea is pretty clear. To maintain the BMEP at 14 degrees ATDC for as long as possible at the end of the powerband.

The theory is that the steady timing retard post powerband allows the deflagation to continue into the exhaust, which progressively heats up the exhaust and increases the speed of sound proportionally. This allows the returning pulse to still be at the right time to keep the power on pipe.

Requirements; A very tight squish clearance, Variable ignition timing, a decent expansion pipe, an insulated exhaust.

Didn't get much time for testing but first go out with the timing at 23 degrees on an 8 degree curve, she did 200rpm more in 4th gear than before. Not bad. Something in it for sure.

When I'm back home (few weeks) I'll continue fiddling with the timing and Kytronic curves but when I'm done I'll do a video of how she goes.

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Last edited by Jack221 on Tue Aug 18, 2020 2:11 pm; edited 9 times in total

this sounds interesting

that looks good have you observed any change in temp?

I have my exhaust ceramic coated. It is supposed to help maintain exhaust temp but probably not as effective as your wrap.

Scooter has been going so well. Really strong and getting to 7700 rpm in 4th almost everytime and a few times over 8300 rpm. Running nice at lower rpm and pulls uphill in 4th. Was so pleased with it. Highest CHT seen was 340F but usually about 310F after a long wide open run.

Unitil............

Started making some funny piston noises at lower rpm. Thought I would strip it and look. Was very surprised to see that there were a few patches of the Nicasil liner missing in my old 210 cylinder. Looks like thats the end of that. Pressure test was not so good too, so something is up in there as well.

That really wasn't long this time and I've gone too far. Full rebuild with a Sport 221 like everyone elses. Staying with the 30mm carb and rotary. Shouldn't need many parts just seals, gaskets and a cylinder. I'll carry on with the 12:1 MRP head, as it stayed cool even when the cylinder fried.

Finally on my way back home. List of parts ordered. And getting quite excited. Not looking forward to doing it in the heatwave in London but got to get her back in one piece.
Went for the MHR in the end. Only way to go for me really. Probably won't do any porting to it for the first go, just a tidy up if anything rough, as I have never run one myself. I do think they are 30bhp straight out of the box so going to be similar port timing to my old tuned one before. Will be nice for the science and see how much more torque there is with the new scavange pattern. Will continue with the rotary inlet, 60 crank, 30VHSH and JL RZ Rh. Build will be starting in a week and on Brighton seafront in two!.

Like the video - never heard of them but my mod education came late via my favorite podcast.

http://www.mistersuave.com/

Jack I’ll probably see you tomorrow at the tea hut Blackheath...i’ll Be on a blue Douglas with 8’' white walls, come and say hello at 10:30 am and we’ll have a cuppa

Last edited by dudley_1972 on Thu Jul 26, 2018 11:36 pm; edited 1 time in total

Not quite home yet. Change country again tonight. That's only a walk from my Sister's. Small world.

We're also doing the night ride through london next saturday so let me know if you're about, probably meet at macDonlads on the old kent road but maybe can pick you up on the way and ride together

I'm here, parts are here, just need a plan.

My MHR measures 45.5 and 31.7 which on a 60mm crank at zero deck gives 189EX and 133TD with 28BD. Now that's quite adventurous. Will have a few days to think about that while I get everything ready. Non engine things to do too. Will have to commit to a base packer by about Friday.


at least 30bhps worth

bit rough here and there


Last edited by Jack221 on Sat Jul 28, 2018 9:01 am; edited 2 times in total

Mmmm. Porn post...

Jack, could you do a port map / layout, in case I'll be adventurous in the future and do some work on my Sport cylinder??

Will do Chris. I would like to leave one searchable on the net. I couldn't find one when I looked. Found someone's MHR dimensions though. Which turned out to be very different from my MHR. Transfers near the same but my exhaust is over 1mm higher. Can't believe there is that much variation between kits.
Overnight thought is its going to rev too high. Will make 9,500 rpm in gear. Nearer 10,500 with overrun. Only need 8,500 for my gearbox and don't really want to snap my conrod. 189 degrees will be so strong on the pipe though......some dilemma.

Ha ha... as you know Craig and I bought 2 kits exactly the same from the same seller within a couple of weeks of each other, look how differently they turned out! Makes you wonder if it's on purpose or what?

Following this with interest. Will you be putting it on the dyno when it's done? You guys seem to have them in every corner store... jealous!

1.0 mm is quite a lot when it comes to ports. Was expecting 0.1 or so differance.
At 1.0mm less there are plenty of revs.
I am going to go in and smooth out the rough parts and drop all the ports to 60mm as this is the 57 cylinder. I didn't want the 60 cylinder as it has no flexibility and could be left a bit stuck if it doesn't pull ok.
The write ups say the 60 cylinder has the 1.5mm fixed on the base but if that was the case with this porting I would be in trouble, so doubt that is true. probably all on the head. Anyway with a 57 I can do what I like.

Going for a 0.6mm base at the moment but might raise the main transfers while I'm in there. The mains are 0.15mm different so need to level them up anyway. This will help flatten and widen the power curve a little more.
So much for not working on it but will not be at its best as it is. And will save one strip down to re-port and re-jet.

Some progress. I had just split it in the frame but took the engine right out to give it a clean. And give more room to do the base port matching. Looks like it doesn't need any. I was surprised. Some parts of the old ports are bigger than the new, so will port the cylinder to the casings instead.

Decided to start off at 0.5mm base and see where the max power ends up. I expect more than 8500 rpm but I hope not much higher.

Refurbished my gear selector. New pawl and new arm. Both were worn. Did a few other jobs too. New tyre, headlight, stator connectors.

Onto the cylinder later today. Will match the base and drop all ports 2mm to 59mm from deck. This should be enough to get near flush at BDC and will do for now. I'll finish them once I know what the final packer is.


New MHR gasket on old 210 ports. It's a match. Near enough.

Re-furb on gear selector

Original black tie wrap still in place ;)

Won't be so long now. That's the cylinder done. Left the ports where they are for now but just moved them all down for the long stroke. I think the packer will end up thin, so no need to go more than 59mm. Going to start with a 0.45mm packer as I have one ready and it's probably about right on paper.

The cylinder is tricky to measure as the casing is rough finished and the ports are not so flat. Some port maps from before and after below.


MHR now 221 ready

MHR as new

MHR ready for 221

Piston ports opened out a little and all edges smoothed

Nice pics and posts Jack.

Bear with, I am a bit of a noob when it comes to porting. I am following your thread as learning for when I do my build.

Comparing your before and after port maps, I see that the bottom of the exhaust port was lowered by 1.5mm. Does the 1.5mm come from half the difference between the long stroke crank and short stoke crank (60mm – 57mm) / 2 = 1.5mm?

Even though not dimensioned on the port maps, I assume that the bottom of the other 7 port windows were also lowered by 1.5mm?

Dumb question maybe, but why not mill 1.5 off the bottom of the barrel and space the head as needed?

When the piston is at the bottom (BDC) all the ports should be open. A little too open is no issue but a step between the port and the crown will create turbulence. Not a great deal of differance but it all counts.

The 1.5mm was just a coincidence. If the ports were exactly 57mm below the top and I was setting the piston flush with the top, then the ports would have needed to move 3.0mm. As they were already 57.5 and I am setting the piston out of the cylinder by somewhere near 1.0mm, only 1.5mm more was required.

Hopefully of some help to you and others. Moving whole cylinder down 1.5mm would affect all the porting and reduce all open durations. This may increase torque but would mostly just lose power and max rpm. Which is the kind of thing we might need to do if the power is too high up.

Might start up today If all goes to plan could be jetting in tomorrow.

Engine build was all pretty normal. Pressure test held 8psi until I got bored. For once there was no work on the clutch. Not sure this ever happened that the clutch lasted longer than a re-build. I always had my doubts about the Superstrong basket thinking that it wouldn't be that super but several years now. Some of the black has worn off but its still like new where it matters. The CR80 plates are the only thing I will ever fit in any PX from now on. Only been in a year or so but still like new too.


Set the squish at 0.9mm. This is about where I left off with the last kit.

Running Haven't ridden it yet but the jetting from before seems to be not so bad to start with. Feels like more rpm than before but we will see once jetted in.

Did 90 miles today. No drama. Few jetting adjustments along the way. Luckily these don't need much running in. And just can't resist not opening up, occasionally. Did 7800rpm in 4th twice today. Just for a second each time. Way more in it. Definately quicker than before. Even with not quite correct jetting she is doing 8400rpm at the top of the power. I think the power band might be about right. no need to urgently change it anyway. That sloping roof on the exhaust port is knocking off more blowdown than I thought it would. Clever these Italians. 4th is pulling uphill as good as before, so happy with that. What an awsome kit. Would take a weeks work to get the old Malossi even near to how the new one out of the box.

Jetting 42&B44 pilot DQ265 atomiser K92 needle @2.5 clip 170 main jet

I've done 150 miles as of before lunch. Running in is over. havn't done any sustained WOT but I've been there briefly and its scary.

My SIP speedo is set fairly close to reality, within a few mph. I saw 87mph on it today. And it wasn't quite done, as there was traffic. The same road used to do 83mph on the old cylinder.

Jetting still slightly rich but getting there. 1/2, 3/4 and WOT to do but the rest is clean.
44 & B56 pilot, DQ263 atomiser, K92 needle @3rd clip, 168 main jet

I'll get the Go pro out sometime this week, so you can all come along. Need to get it recorded in case something breaks. No picture it didn't happen.

Sounds good!

Apart from raining today, I spoke a bit too soon. Riding yesterday we were going great until I was on the motorway doing more high speed runs (it's just so addictive) and noticed although she sounded fast, the speedo didn't exactly show it like what is now usual. Clutch was slipping. About 500 rpm over revving. bugger.

Stripped the clutch quickly and the plates are fine. Checked the springs with some new ones and they are shorter and softer, according to the finger squeeze test.
This clutch takes 10 springs and had 5 SIP XXXL springs and 5 SIP XXL had more of both so put in the same again but new. Raining now so test will be tomorrow. Harder to pull the lever so hopeful speed is now back to terrifying.


Squished

How many miles on your suspect springs? Just wondering how long the clutch will live with the same setup as before.

Is that a Honda plate clutch?

To answer both together, the springs were not changed when the Honda CR80 plates were installed. They seemed ok. Had done about 4000 miles on these springs. Probably about 1000 on the CR80. I blame the MHR, it just goes too well

Still raining but got out between showers. You will all be relieved to know the clutch seems to be fine now.

Jetting fiddled with, 48 & B56 pilot, DQ262 atomiser, K93 needle @2nd clip, 170 main jet

Another jetting test yeasterday. Getting really happy with it. Not quite so fast now but temperature never runs away at any throttle position. mid might be slight rich and WOT slight weak but very close now. More riding and more fiddling required

58 & B68 pilot, DQ261 atomiser, K93 needle @2.5 clip, 170 main jet

Still very happy with progress.

Set the jetting to hold the temperature down to about 280/300F at all points. This is rich but proves I have control of the temperature.
Now the fun begins.
Last few days I have been weakening the jetting to allow 320F at WOT. Together with adjusting the timing and Kytronic.

60 & B60 pilot, DQ262 atomiser, K93 needle @1.5 clip, 165 main jet

Seems to be settling down nicely. Will continue fiddling with the settings but very close now.

I did several videos but the wrong kind of sun is making too much glare for the speedo. Had to do 5 runs to get this one but I'm not complaining. This wasn't the quickest but the only one where the speedo can be read. Really is some scooter now. Great to ride.

Back home again. Still think there is a bit more in this. Not going to take the cylinder off yet, although I do think a small packer change is required.

Will fine tune the jetting and Kytronic and let the temperature up slightly more.

Was all going so well but something had to break. Didn't think it would be this.

New crank, flywheel and bearing....at least.

Scooter has been running so strong but for the few days up to this there was some strange vibration at high rpm. When it came off, it felt exactly like a seize up but the only silver lining is that the bore is fine, not a mark on it.
Was a few days ago now, so over the shock and the embarrassment of arriving home on a recovery truck. Now working on a list of parts and of course a few improvements

Yikes.

Yikes - that sucks! What were the speeds you were typically running? You're in KPH, correct? From the video from August it looked like 80-90KPH consistent. I'll be watching to see what you decide to do as far as improvements. It looked far superior on the improvement front compared to most!

No that's mph in the UK although reads a few mph over, so not that amazing but over 80mph in any case.

Yikes indeed. Can't believe the crank actually snapped but that crank is actually about 6 years old and has taken considerable punishment in that time.
If you count the many millions of rpm, stress and flexing, metallurgy wise, its really held up quite well. Still doesn't help with the cost though.

Snap.


(pun intended)

Unbelievable, yours has snapped in nearly the same pattern. How long ago was this snap and what set up was it on?

You think the 1.6kg flywheel is too heavy?

More of the keyway was left on my crank than yours, that seems to be the only difference. That was June 2016... it was a Mazzuchelli.

Interestingly, a mate did a similar thing to his. But his was new. The only thing that we both did was start the motor using a drill and socket... something that neither of us do now. I'll see if he has a picture.

Still seems like a very similar snap pattern. I hope to not be seeing it again any time soon.

I assume starting with a socket means yours was on a track bike? Wouldn't imagine this is a great idea but doubt it would cause any issue, especially with the welded pin.

My crank was a modified Mercur but new one most likely to be Mazzuchelli, which is the same now. Will try to buy something I don't need to do to much work to before it goes in.

The only issue remaining is the new flywheel. Same or lighter? A much discussed subject on here. The old one was 1.9kg, as it is a full frame road scooter. Was thinking to go 1.6kg but she's quite powerful now (35bhp+) and worried a lighter flywheel will do more damage to the rest of the engine. I have a few weeks to make my mind up but any input welcome.