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Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
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Discussion Starter · #1 ·
Hi lads,

I got my hands on a TurboKit exhaust which looks like a Polini 6.2 kind of pipe. The seller could not tell exactly, but I was hoping it might fit my cag because here in the EU go-fast exhausts are all sold out. Also no luck on the China websites for faster cag pipes, so this is my best bet.
No usefull info on the website of this manufacturer, but the pipe looks like good quality.

So the idea is to try and fit it without cutting it up and to see if it will give me some gains. My setup now is a BB kit with 2-pc head, 2 shoe clutch, stock pipe with protruding bit removed and stock carb. It runs 28 mph on 6-68 gearing at 9700 rpm atm.
Did a mock up and it could fit if I remove two of the cooling fins on the cilinder head. Hopefully it will not give too much cooling problems. Hoping to get it fitted this weekend...

test fitting
Wheel Tire Crankset Bicycle frame Bicycle tire


Small issue clearing the cilinder
Tire Automotive tire Motor vehicle Hood Wheel


Test fitting, here the pipe is too much outward. But it looks like it will fit.
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Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
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16 Posts
Discussion Starter · #4 ·
Looks great if that is a PBU head I would not modify it I would get a different head simply because of the rarity of the part.
Mmm, no it is not a PBU head kit. It is China made. However, all new head kits look different to this one indeed.
Will start grinding away tonight.
 

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Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
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Discussion Starter · #5 ·
I took the Dremel out and shaved off some cooling fins and made a new bracket for the pipe. It just sits clear of the cross bar on this L7 frame. Now to put on a new fuel line and see what this pipe does on this setup, weather permitting.

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Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
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16 Posts
Discussion Starter · #6 ·
So I also had a peek inside the cilinder with the exhasut off. I notice that there is about a millimeter of piston still showing at BDC. Now I don't have a clue about porting and timings, but would it need raising the cilinder to have it open completely? Or would that just mess up port timings and my squish?

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The compression is too valuable anything you do to change it will effectively lower the compression at TDC it's better to widen the exhaust port to compensate...
 

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So I also had a peek inside the cilinder with the exhasut off. I notice that there is about a millimeter of piston still showing at BDC. Now I don't have a clue about porting and timings, but would it need raising the cilinder to have it open completely? Or would that just mess up port timings and my squish?

View attachment 161232
Don't care about this mm. Did you even measure you squish?
 

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Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
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16 Posts
Discussion Starter · #10 ·
Ok, thanks for the info guys. Indexing the piston sounds like marginal upgrade, only to do if other mods have been done.

I installed this head kit many moons ago. Like 2006:) and it was my first cilinder and piston swap. Pretty sure I measured the squish, but I can't remember what it was.
What I do know that it feels like a lot of compression when pulling the starter cord, especially compared to the stock cag.
It ran great all those outings on the karting track back than, so I will leave it for now.

Out of interest; how much should I widen the exhaust port? Also 1 mm? Should it be tapered or straight?
 

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Yes just enlongate it a bit don't raise it up just be known that the biggest hindrance in these engines is the flow path between the intake Reed cage and the feed ramps
 

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Lucky 7 with BB head kit, 2-shoe clutch w \zocchi springs, flywheel mod, lift-plates
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Discussion Starter · #12 ·
Alright, I will do so when its time to take the cilinder off.
How many hours would you run these engines before you replace the piston or piston rings normally?

And what exactly are the feed ramps? Sorry for dumb questions..
 

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I run them until they start losing power or they get so clickyclacky it sounds like its going to blow it's always the same problem piston rings and cylinder wasted, wrist pin bearing, clutch side crank bearing.

These engines are so inexpensive sometimes it's not even worth rebuilding and you're better off getting a new one and starting with a blank canvas 60$
 

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New is nice having around. I have so many new cylinders and pistons, gasket, carbs, I am in a position to rebuild but not a lot are.
Yea but you run 40:1 I'm running 50:1 sometimes 60:1 on dominator at 40:1 you probably get about 3 cylinders per 1 bottom end am I correct on my estimates ?
 
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