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Veni, Vidi, Posti
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charlieman22 wrote:
Funny you mention. I have never used. Sip Road stayed in place by tightening the nut.

But I just came back and it sounded funny.
Looked- it has slipped down on the ex. stub.
Is that a thing?!
Do I have to weld on some spring holders of some kind?

Funny - I have always been miffed by those springs.
When I look at them - I think - well - that isn't going to hold anything.
Am I about to find out differently?
What do you hook them on the motor?
Definitely a thing. Size of the stub tends to vary for one, and aluminium stubs get deformed over time for two... so yes the springs really do work.

You hook to the front/lower cylinder cowl/flywheel cowl screw with a small plate - usually supplied with a SIP road. The other side goes to a hole you drill through a head fin. Kind of helps if you use the proper exhaust springs where one end is free to rotate.
I'll get a pic or two shortly, if you agree in advance to ignore my welding "skills".
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Nedminder
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Ha! you should have seen the welds I slapped on the rebuilt mount for the box...

Thanks Ginch. That would be great.
I'll put some on in the morning - I still have the ones that came with the SIP road two - sitting in my tool box for 2 years.
Finally get to use em.
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Veni, Vidi, Posti
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I probably put this hook in not quite the right spot, but it works. Used a flat bit of metal rather than a wire hook because it would be easier for me to weld.
The little plate I re-drilled because I could find my spring stash when I did this...

The hole in the head fin is pretty obvious where it needs to go. And usually there is limited space where you can access it anyway (when it's in place).
Polini box
Polini box
On the SIP road
On the SIP road
⚠️ Last edited by Ginch on UTC; edited 1 time
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Veni, Vidi, Posti
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Christopher_55934 wrote:
I was looking at these, for spring mounts on motor.
I get mine from ebay kart shops - bit cheaper, and they usually have a selection of different lengths (which hide from you when you actually need them).
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charlieman22 wrote:
Funny - I have always been miffed by those springs.
When I look at them - I think - well - that isn't going to hold anything.
When you see how taught those springs are you'll understand how much they do hold. Seriously hard to get on and off without hurting something.
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Like I need another gashed knuckle.

Guess I'll use sip road 2 Loop placement.

Need some sorta quick release.
Don't wanna make removing exhaust a science project.
Gotta ponder that one.
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charlieman22 wrote:
Need some sorta quick release.
External inline image provided by member with no explanatory text
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charlieman22 wrote:
Need some sorta quick release.
Don't wanna make removing exhaust a science project.
Gotta ponder that one.
A decent pair of round nose pliers (used closed) or large screwdriver (the shaft) is all you need. Something rounded to put in the spring hook with handle so you can use controlled strength to stretch it.

Technique > tech on this one.
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Ginch wrote:
https://www.lambretta-teile.de/Exhaust-flange-mild-steel-with-Viton-ring-to-weld-on-Vespa-Sprint-PX80-150
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charlieman22 wrote:
But I just came back and it sounded funny.
Looked- it has slipped down on the ex. stub.
Is that a thing?!
Do I have to weld on some spring holders of some kind?

Funny - I have always been miffed by those springs.
When I look at them - I think - well - that isn't going to hold anything.
Am I about to find out differently?
What do you hook them on the motor?
With vibration into the pipe and pressure waves it totally makes sense that a rigid clamp fixture will move. The springs give that flexibility and instead of slipping down the exhaust essentially slips up and tighter as it rattles around.
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bodgemaster
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Definitely use the springs.
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Jet Eye Master
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pheasant plucker wrote:
charlieman22 wrote:
Need some sorta quick release.
Don't wanna make removing exhaust a science project.
Gotta ponder that one.
A decent pair of round nose pliers (used closed) or large screwdriver (the shaft) is all you need. Something rounded to put in the spring hook with handle so you can use controlled strength to stretch it.

Technique > tech on this one.
Getting springs on and off can be painful and using screwdrivers and pliers outright dangerous. However, buy one of these and you could do it with one hand. Taking off the exhaust becomes a pleasure.
https://www.amazon.co.uk/PQZATX-Exhaust-Spring-Puller-Motorcycle/dp/B089K19XX3

Next top tip. Drill a hole in your bottom cylinder fin and in the head fin and the springs sit better and less angle.
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Quote:
buy one of these and you could do it with one hand. Taking off the exhaust becomes a pleasure.
Finally - suggested something useful.
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Jet Eye Master
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charlieman22 wrote:
SC rods are backwards - so that 28 is actually richer than the 30 I was running on the smaller carb.
The move up from 25mm to 28mm required a richer rod (tho it has a smaller number...)

Yeah - I was super pleased with the feel.
Having to just about re-build the Polini box from scratch (only half kidding) to make it fit with my subframe.
Fab is done.
Let paint dry - so I could assemble (again).
Got out for quick trip in the hood.
Feels great at lower RPM.
Will be interested to see how it tests tomorrow.
Forgot the rods were backwards. Going a few sizes richer and increasing power, simply means the 25 was too small.
If the Polini works better at high rpm it will need richer still. Exhaust could actually make a bigger difference. Meaning even more effective blowdown but we know how to fix that.
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Jack221 wrote:
Getting springs on and off can be painful and using screwdrivers and pliers outright dangerous.
Pfttt. Says the guy who sits on a 40hp 10krpm 2T timebomb?

I guess if you are on and offing it a lot then that's a worthy investment. 'Cept not even I would pay for a tool that simple to make.
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Ok - exhaust is on.
Below are "best runs" rather than means.
I'll get some more in - but this tells the story fairly well.
The good news: power is up - and it is in earlier.
The bad news: there is a clacking sound and Im concerned its a rod nock. Yup.
Timing not good. Have a x country trip in the works and plan to bring the scoot.
Leave in 12 days.
Yikes.

How can one check for a rod nock without pulling the jug?
(Is the answer to this - pull the jug?)
*Edit - see next post - I had a nocking alright - just not a rod nock!
Polini vs Sip Road II.  Getting that 12HP at 5K now.  Very nice.  Orange is Pollini.  Green is SIP
Polini vs Sip Road II. Getting that 12HP at 5K now. Very nice. Orange is Pollini. Green is SIP
Power is all in at 7K - has brought me back to stock BGM cylinder feel - with greater over all HP.  Blue is untuned BGM cyl/Sip RdII
Power is all in at 7K - has brought me back to stock BGM cylinder feel - with greater over all HP. Blue is untuned BGM cyl/Sip RdII
⚠️ Last edited by charlieman22 on UTC; edited 1 time
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charlieman22 wrote:
Ok - exhaust is on.
Below are "best runs" rather than means.
I'll get some more in - but this tells the story fairly well.
The good news: power is up - and it is in earlier.
The bad news: there is a clacking sound and Im concerned its a rod nock. Yup.
Timing not good. Have a x country trip in the works and plan to bring the scoot.
Leave in 12 days.
Yikes.

How can one check for a rod nock without pulling the jug?
(Is the answer to this - pull the jug?)
Good to see the pipe did what was expected.
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Veni, Vidi, Posti
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UTC quote
Great result! Would have been nice to have 'clawed back' some of that earlier power that you use in everything but your high-speed runs, but can't have everything.
Suspect there will be a bigger pre-reso hole with the MHR... remains to be seen.

When the big end went on mine, there was no knock (spelling) noise, just something that felt like a soft seize. A gradual reduction of power until I stopped.
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Nedminder
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Quote:
A gradual reduction of power until I stopped.
That hurt my heart.

The nock was the exhaust - bouncing on the spring - hitting the subframe.
I say spring - because I decided to put only one spring on - allowed a quick weld and attachment while still on scoot.
I was too soft on the header clamp - so it was sliding up and down.
If my scoot suffered from half of the things I imagine it has - it would be a disaster.

I will try the lift on this cylinder.
Recoverable.
Just a gasket and a bit of motoseal/hondabond/threebond/Permitex...
And when I say touch...


So drivable like this - so much juice in the first 1/4 throttle I gotta be careful - but all in at 7K is just a lil too early for me.
May have to trade a little.
Quote:
Suspect there will be a bigger pre-reso hole with the MHR... remains to be seen.
I have same suspicion on MHR - but also suspect there is a grunt set up to be had with it that would trade some max HP but make it a monster.
If we can ever convince jack to sketch up some options on exhaust shape and explain to us how it would alter our power band.
For convenience - I've provided a pallet below to educate us with.
Sketch pad
Sketch pad
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Jet Eye Master
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Polini box doing exactly what was hoped for. 28mm carb increased power on the same manifold. Big end knock turned out to be nothing. Where does your luck run out Razz emoticon
Must be great to ride now. P200 torque with actual speed.

Let's focus on the BGM for now. One last push and it's done.

It's in here somewhere but can you remind us of where the BGM timing is and what the packer lift suggestion was?
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Would take a librarian to find it.
Luckily - I posted in bold so I stood a fighting chance.
Quote:
Here are the numbers - so I have them recorded:

Actual measure: 38.03
.5 base with 1.3 head gasket and 3.97 head insert (.8 squish) = -3.26
38.03-3.26 = 34.77
= 124.5/181.5/28.5
to get here - I went from .2 to .5mm base gasket - and took the head gasket down from 1.5 to 1.2 in order to maintain the .8 squish.

Think you had proposed another .2MM to .3mm of lift.
Quote:
For the BGM and your needs (torque) you need over 180 but less than 185 (Just between us this is like a magic number). 124.5 is sufficient. Can be adjusted with head gasket, so that won't affect squish by much that matters.
.3mm lift would give 126/183/28.5
This was the stock BGM out of the box with .2 base lift
This was the stock BGM out of the box with .2 base lift
This was the timing with .5 base lift, and 2MM of port grinding on the exhaust to bring it up higher
This was the timing with .5 base lift, and 2MM of port grinding on the exhaust to bring it up higher
.3 additional lift should put me here
.3 additional lift should put me here
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Ginch wrote:
I probably put this hook in not quite the right spot, but it works. Used a flat bit of metal rather than a wire hook because it would be easier for me to weld.
The little plate I re-drilled because I could find my spring stash when I did this...

The hole in the head fin is pretty obvious where it needs to go. And usually there is limited space where you can access it anyway (when it's in place).
Is the spring mount on the exhaust really necessary, or does the exhaust go on tight and loosen up after a while? Nice job on the welding for the two materials you're working with.
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My SIP road II had a different style clamp and it never slipped down in all the abuse I gave it.

The Polini box will not stay in place without the springs - on my set up anyway.
I didn't want to deform the head exhaust outlet - so springs made sense rather than king konging the tightening job.
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CM are they off a bit on the shape/allignment of the exhaust for a comfort fit?
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Not off alignment or shape.
Polini Box is a slightly larger ID I suspect.
Just doesn't get the friction/holding power the SIP pipe did - which had a snugger fit.
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FMF spring tool has been the best design that I've ever used. https://www.rockymountainatvmc.com/parts/fmf-pipe-spring-puller-tool-p
⚠️ Last edited by whodatschrome on UTC; edited 1 time
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Molto Verboso
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charlieman22 wrote:
Not off alignment or shape.
Polini Box is a slightly larger ID I suspect.
Just doesn't get the friction/holding power the SIP pipe did - which had a snugger fit.
Wonder if you can find or make something like this for the BGM stub:

https://www.sip-scootershop.com/en/products/exhaust+stub+gasket+kit+sip+_13014000
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Whodat/Jack: Spring tools look mighty useful. Tks - put that on my ever present Amazon account. I dont even bother to close the browser window any more.

SWA - Tks. Funny - as soon as I saw that - I remembered buying it on my very first trip to SIP - so I have one! The good news is - The clamp snugs the exhaust well enough - just not well enough to hold it without the help of the springs. Now that I have a spring on it - I don't think I will need the stub adapter - but if I do - thanks for reminding me!
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charlieman22 wrote:
Would take a librarian to find it.
Luckily - I posted in bold so I stood a fighting chance.
Quote:
Here are the numbers - so I have them recorded:

Actual measure: 38.03
.5 base with 1.3 head gasket and 3.97 head insert (.8 squish) = -3.26
38.03-3.26 = 34.77
= 124.5/181.5/28.5
to get here - I went from .2 to .5mm base gasket - and took the head gasket down from 1.5 to 1.2 in order to maintain the .8 squish.

Think you had proposed another .2MM to .3mm of lift.
Quote:
For the BGM and your needs (torque) you need over 180 but less than 185 (Just between us this is like a magic number). 124.5 is sufficient. Can be adjusted with head gasket, so that won't affect squish by much that matters.
.3mm lift would give 126/183/28.5
Good suggestion. Another 0.3mm puts it at exactly 126. And that's more like where it needs to go for the next level. Blowdown reduced by 0.25 too. This should further increase torque and lengthen the power band a bit. Results by tomorrow?
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charlieman22 wrote:
Whodat/Jack: Spring tools look mighty useful. Tks - put that on my ever present Amazon account. I dont even bother to close the browser window any more.

SWA - Tks. Funny - as soon as I saw that - I remembered buying it on my very first trip to SIP - so I have one! The good news is - The clamp snugs the exhaust well enough - just not well enough to hold it without the help of the springs. Now that I have a spring on it - I don't think I will need the stub adapter - but if I do - thanks for reminding me!
My Sito+ that has the slip on O-ring flange thing welded on. I ordered the stainless exhaust spring hooks off of eBay. Even though they came from China, I'm still impressed with them. It was a bag of 25 or maybe 50 of them for something like $10? I also use the short Akrapovic springs.
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parallelogramerist
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And I buy O rings in bulk from https://www.theoringstore.com/store/
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Whodat - pretty cool.
What's the deal - do you cut the pipe and then weld on the o ringed portion?
Hard to tell - cause the welding looks factory.

Jack - will likely drop the motor for this one.
Replace the clutch wear plates at the same time.
Drain oil and give it a good clean.

While I have it out - I'll fit the Malossi and see what kind of challenges I'm going to have with the case to cylinder transfer ports.
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charlieman22 wrote:
Whodat - pretty cool.
What's the deal - do you cut the pipe and then weld on the o ringed portion?
Hard to tell - cause the welding looks factory.

Yup. About the top 1" to 2" of the exhaust gets cut off. The exhaust clamp gets removed first though. All it takes is grinding off the spot welds you do it. Then push the new SIP exhaust coupler thing over the cylinder's exhaust stub (but don't install the O-ring just yet). Fiddle around with exactly where the exhaust header fits best inside of the coupler (like cutting lumber, it's easier to make multiple cuts that won't remove too much material. It's difficult to add material if you cut it too short). Then weld all the way around the new coupler. Tack weld on the spring hooks. Drill some holes in the cylinder fins. Rattle can some high-temp paint. Grease up the O-ring before installing it, and Bob's your uncle.

I don't have any good pics of mid process of the welding, but I got one pic of where I needed to grind a little more clearance on the out edge of the coupler.

It's a great mod when having an aluminum cylinder. Clamping a steel pipe on aluminum can damage it over time. Especially since our 2 stroke scooters vibrate so much.
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Nedminder
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62 VBB1T Round Tail W/ leaner sidecar
Joined: UTC
Posts: 4109
Location: california
UTC quote
why do we ever have to go to work?
This is sooooo much more fun.
UTC

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4605
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4605
Location: London UK
UTC quote
As long as there's no gaps in the gasket I wouldn't worry about matching the Malossi ports too much, if you can without going through great. If you can't won't make much difference for your set up.
OP
@charlieman22 avatar
UTC

Nedminder
62 VBB1T Round Tail W/ leaner sidecar
Joined: UTC
Posts: 4109
Location: california
 
Nedminder
@charlieman22 avatar
62 VBB1T Round Tail W/ leaner sidecar
Joined: UTC
Posts: 4109
Location: california
UTC quote
^ Makes sense.
Not sure if my gasket surface will cover or if I will have an open spot.
My even try my hand at a small tig weld if I just need a few MM to add...
Will cross that bridge when I arrive.

Am really surprised by how much the pipe dictates the motor rev range and power band.
The Polini box is unquestionably torquier lower in the rev range.
Its as if the cylinder was lowered.

For my driving - I find the 7K peak just a hair too low.
Keep in mind I have geared it fairly low - to allow for the sidecar - so I hit 7K pretty quickly.
Peak at 7500 to 8K is a bit more to my liking.

Below is an interesting chart from the inter webs.
It lays out some timings and for transfer and ex. ports.
If you match RPM of the two charts - in the closest thing they show - its pretty close to our target of 126/183. Similarly - if you match as close as you can the 6500RPM (with the 7000 RPM) it is close to where the BGM timing started at 123/173
Forum member supplied image with no explanatory text
UTC

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4605
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4605
Location: London UK
UTC quote
Good luck with tig. Can be a bit all or nothing. Could actually save time sending it to Safis for welding.

Charts look like the work of Mr Bell from a very long time ago. Not sure what you're seeing but looks like some very fuzzy imagination to line that up. These are figures for max power not max rpm and based on 40 year old exhausts, angles and cranks. ie. +/- 5 degrees or irrelevant.

Raising the packer will up the max rpm. Should give the right result. And that being more rpm without torque loss.
Ready by tomorrow?

Btw I just down tuned my 221 and it made absolutely no difference. With the hornet245 on I can still get 11,000 rpm if I hold it out in 3rd like you do. Struggling to make it slower. I'll try again tomorrow.
This further proves, as you have seen on yours, the exhaust port size/shape/angles are half the story and the exhaust is the other. Both have to be suited to the purpose to get the desired result.
OP
@charlieman22 avatar
UTC

Nedminder
62 VBB1T Round Tail W/ leaner sidecar
Joined: UTC
Posts: 4109
Location: california
 
Nedminder
@charlieman22 avatar
62 VBB1T Round Tail W/ leaner sidecar
Joined: UTC
Posts: 4109
Location: california
UTC quote
Quote:
Could actually save time sending it to Safis for welding.
That one tickled me a little.
Probably.

Charts:
Quote:
Not sure what you're seeing but looks like some very fuzzy imagination to line that up
Here is the perspective.
For most of us - timing numbers are a mystery.
You make them higher - it get's peakier. ok.
Higher blow down numbers can narrow the power band. Gotcha.

But what transfer numbers should go with what ex. port numbers is less clear.
The BGM came with 123 transfers and 173 exhaust.
Interestingly - the charts would suggest a similar combination.
We moved my transfers up to 124 with exhaust going to 182
Again - that is within the charts match for 8K RPM.
Now we are looking at 126 transfer - chart suggests this would match with 184-186 exhaust timing.

I wasn't so focused on what RPM max power would occur.
Clearly the exhaust has a big say in that.
But the ranges given in the chart for combinations of timings seem to be where we are headed and have been - at least within the ball park.
That's news for some of us.
Quote:
This further proves, as you have seen on yours, the exhaust port size/shape/angles are half the story and the exhaust is the other. Both have to be suited to the purpose to get the desired result.
becoming more clear for me - though it was surprising.
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