Technical Rotax max performance

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1995dj

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David joynson
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Rotax max
Engine
125 max non evo
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Dart
HI, new to karting to support my son. We have picked up an old dart rotax kart. I've used the interweb and been through and cleaned the carb (blocked pilot jet) reset float height etc. Rebuilt the power valve, new diaphram etc. Aligned the wheels, new pads new used tyres.
Took the kart to llandow and had a fantastic afternoon however felt the performance was not great with the twin engine honda^s being similar.The kart maxed out at 12ish k on the back straight and pulled well over 8k but slow to pick up. The engine is a sealed early engine with a 12.5 carb. Its running a 168 main and 30 30 jets. I've put a compression tester on it, carb removed and only see 75psi which is half what I'm reading on the net. Am I doing something wrong as I'm surprised the engine runs being so low ?
Should I pull the head and barrel off and measure or ate there other things to try first ?
All advise great fully received
Regards dave
 

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1995dj

Community Newbie đŸĩī¸
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GL128LS
Name
David joynson
Skill Level
Novice
Class
Rotax max
Engine
125 max non evo
Chassis
Dart
Update - borrowed another gauge. This read 135 psi on the cold engine
 

Daver5

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Good news the second gauge worked.

I'm no expert in the slightest but I was having similar issues.

I wound power valve all the way in and then out 5 clicks
Then I changed to a 158 jet and finally see 14000 rpms
 
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1995dj

Community Newbie đŸĩī¸
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55
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GL128LS
Name
David joynson
Skill Level
Novice
Class
Rotax max
Engine
125 max non evo
Chassis
Dart
Many many thanks for your reply. My pv has 6 clicks per 360 degrees and 5 full revolutions in to out. The pv is set to the correct length and has new diaphrams o ring and spring.
5 clicks would not be 1 revolution
Regards
I've jets on order :)
 
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Daver5

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I have no idea how it works tbg but 1 of the old boys at rye house wound my pv all the way in on the red bit then out 5 clicks.

Was night and day difference
 
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