1997 XP 787, Too much compression?

[Rubends83]

Hi there,

I just rebuild the top end ( pistons and carbs ) of my xp 1997 and now i have the following problem:

When the sparkplugs are out the engine cranks like normal no problem, when the plugs are in the engine jams... I have tested the compression and it says about 160-165 psi. I guess that this is too much and the starter cant swing the engine around? Could this be due to a faulty base gasket? I used Prox pistons and gasketset....

Hope you guys can help me out...

Thanks

 

[ZeroTolerance]

I'm running my heads at 175PSI with no problems so the PSI isnt your issue.
I'd make sure your engine is getting oil probably is but just make sure. Sounds too me like a timing issue or the starter or battery. Check the cranking amps on your battery. Also make sure you set the timing correctly.

 

[stickshift69]

Sounds like a weak battery

 

[kustomkarl]

Be sure the battery wires are good and clean. Check the ground going to the starter area of the engine too, as it need to have a good connection. If you are in doubt of teh battery have it load tested at like Auto Zone for free. If it has a bad cell or 2, it won't have the amps to turn the engine over. Afer you get it fired up and broke in, do a compression test to have a accurate number. It ideally should be at 150psi.

I see this same problem at least 20 times a week here on the forum.

Karl

 

[Rubends83]

Thanks for your help but the trouble isnt over yet :reddevil:

I have checked everything, battery, startercables, starterconnection etc.. I even put the 12v straight onto the starter and it was a little bit better but still not good enough... Could it be the starter?? Do these things break down? And is it possible to rebuild them or do i have to buy a new one??

Let me know

thanks

 

[kustomkarl]

It might be the starter, pull it and check it out.

Karl

 

[stickshift69]

With the spark plugs in place try turning the engine over by hand, little difficult tho.

 

[timmyboy76]

Thanks for your help but the trouble isnt over yet :reddevil:

I have checked everything, battery, startercables, starterconnection etc.. I even put the 12v straight onto the starter and it was a little bit better but still not good enough... Could it be the starter?? Do these things break down? And is it possible to rebuild them or do i have to buy a new one??

Let me know

thanks

those motors, new/rebuilt, should have 160psi. Recheck the RV, make sure the valve is set at 147*/65*. think its ur starter though. Have a shop take a gander/rebuild it.