Jump to content
Sign in to follow this  

xr100 backfires but won,t start after rebuild

Recommended Posts

I bought two basket case xr100's one is a 82 the other a 94 I took the crank out of the 94 and put it into the good cases of the 82 changed the flywheel and stator over to the 94 cdi system. The cam timing is correct according to shop manual. I dissembled and cleaned the carb checked to make sure the factory jets and air screw settings where correct. Clean air filter, Clean fuel petcock , clear fuel line so I can see the fuel going into the carb. I have good spark and fuel is getting into the cylinder (wet plug). when I try to start I get a backfire after several kicks. Leads me to believe key is sheared , doubled checked and it is fine. Any ideas???????

Share this post


Link to post
Share on other sites

when u checked the cam timing did u check valve clearances. my xl 100 does this too and i eventually concluded it was the rings (still waitin for the parts)

but the bike would fire once and then nothing. and if u put ur finger over the spark plug hole after a coupple kicks it should push ur finger off

Share this post


Link to post
Share on other sites

How did you setup the cam timing? Look at the manifold for cracks.

Share this post


Link to post
Share on other sites

Double check the valve clearances. Had the same prob w/ mine and the valves needed loosening.

Share this post


Link to post
Share on other sites

I checked and adjusted valve clearances before I put the motor back in the bike, It also has a fresh cylinder , new piston and rings. I thought about the intake as well swapped that out and triple checked for cracks.

I'm thinking bent valve, I've got another head I'm going to try to put that on tonight.

Share this post


Link to post
Share on other sites
How did you setup the cam timing? Look at the manifold for cracks.

I set the cam timing with the flywheel on the T mark, cam lobes down and "o" at the top of the cam sprocket. I used to race a 200x three wheeler back in the day and I could tear that motor down and put it back together in my sleep.

Share this post


Link to post
Share on other sites

Found out the problem, had a bad head=no compression. Put the other head on and it fired right up. Now I'm working on putting lights on it. Thanks for the help.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...