95psi compression and wont start

[snowrascal]

hi i have brought a Peugeot xp6 it has a 70cc kit on and upgraded crab (25mm)
it won't start kick start at all-clean fuel, got spark, new carb.
i ran a compression test and got 95psi
could the compression be the problem as it still won't run?

[The Shaggy D.A.]

[stevo as b4]

25mm carb?

Too big for a sensible road bike, you'd need a full race 14000rpm 70cc motor to even start to make a carb that big work well enough to be useable.

[snowrascal]

yeah a 25mm carb, i have just brought it and thats what was on it
thanks

[Hong Kong Phooey]

You say it's got compression and spark so logically fueling is the missing piece of the puzzle.

How sure are you that it has spark at the right time, and how was compression tested? Have you just fitted carb after it was previously running?
____________________
'81 CG125, '97 FZS600 : '99 CBR600F4, '09 KTM RC8

[P.addy]

95psi...
What does the manual say, I'm sure there is one online telling what to expect psi wise. It would be better to bang it back to 50cc and standard and work from there.

[Luckyfish13]

95 psi should be fine...rule of thumb is 100...I once worked on a Honda vision scooter with fuel injection which started first time every time at 40 psi...

[Rogerborg]

[P.addy]

[snowrascal]

thanks for the replies
compression was tested with a standard engine compression kit, its the same carb and i didn't receive a manual. its a two stroke. i have another look today

[bikenut]

xp6 a water cooled 2 stroke, so a relatively low compression pressure, due to the ports.

So 95 psi sounds relatively good, what does the book say?

Check when the spark happens with a strobe timing light, to rule a sheared flywheel key out.

I presume its impossible to fit the reed valves in the wrong way, any blow back thru them?

How is the exhaust system, not blocked ?

I assume the piston is fitted the correct way. :karma:
____________________
nuts about bikes

[Luckyfish13]

[bikenut]

You have a similar thread with a 50cc unit, does the big bore conversion make the classic "2 stroke noises" and pump ?

The 50cc unit didn't want to run, so I assume you fitted the big bore and hoped it would run? but doesn't, so........

Does it pump and make the pumping noises some of us know and love?
____________________
nuts about bikes

[Luckyfish13]

[neptune8]

Suspect fuel problems? Here is a quick and dirty test. Pour about a quarter of a teaspoon of fuel down the plug hole.Replace plug, and operate kickstart. The engine should then start and run for several seconds. If it then stops, it is probably fuel probs.
____________________
Enjoy yourself, its later than you think