Jump to content
Steve Wagner

XR100R 1985 no fire

Recommended Posts

To check the crank, just look for circular marks on the taper.  There should be zero marks.  Plus you can see damage on the flywheel as it spins around the key.  But, if it's not backfiring, it's probably didn't spin. If it gives you much more of a headache, you can easily swap it for a CDI ignition.  

Edited by socalxr

Share this post


Link to post
Share on other sites
On 9/30/2018 at 11:50 PM, Alexxxx said:

What number is stamped on the flywheel?

F130- ??

F130 is stamped on flywheel. Installed a new aftermarket carb on it, and switched spark plug cap to a resister cap and she runs!! Idles ok but at full throttle it wants to stall and backfire and lose power. So some fine tuning to be done there. 

Thanks again to everyone’s help. I’m sure as I get deeper into this project I will have many more questions

Share this post


Link to post
Share on other sites

Just wanted to ensure you got the correct flywheel F130-58 for XR100 and not F130-54 for XR80 with different timing marks.

Now that your engine is running, it's important to check ignition timing with a timing/strob light. That is extremely important because even small deviations lead to the above described running symptoms.

When timing is done you may think about the carb and other things.

 

Btw., the engine runs with or without resistor(s) in spark plug or cap. That resistor is only to eliminate distortions in electronic devices at the environment.

There are lots of faulty plugs and caps out there, even new ones.

Edited by Alexxxx

Share this post


Link to post
Share on other sites

I think it is 130-58. I do need to fine tune the timing. When I got it going it started clicking under the valve cover. Shut it down and removed the cover to find the cam chain sprocket had loosened. Tightened the sprocket but now I think cam chain is loose. Didn’t have time to investigate further but will have to look at before starting up again

Share this post


Link to post
Share on other sites

When the cam chain sprocket loosened it resulted in the woodruff key getting sheared and messed the timing. Got a new key and learned the hard way I need to torque the flywheel nut before I ride the bike, sheared the damn key again. Before it sheared the key it was running well but does feel like the clutch slips. Revs up but power stops making it to the rear wheel. 

Woodruff, clutch, fork seals, steering head bearings and rear shock bearing and she should be good to go.

Share this post


Link to post
Share on other sites

Is there a situation where a bike can have decent compression but still need a rebuild? The few times I’ve had the bike running it doesn’t run well, and there is a definite clanking going on. I’ve changed oil twice and a lot of metallic in it. Just gauging opinion before I tear it down. 

Share this post


Link to post
Share on other sites

It’s possible that the piston skirt broke off and that is the metal you are finding. The skirt breaking below the rings would allow the bike to still have compression and could explain the “clanking”. If you are finding “a lot” of metal in the oil I think it best to tear it down and see what is going on.

 

Share this post


Link to post
Share on other sites

Update on this project. After all the work done to it the engine started a couple times and ran horribly and now won’t start at all. So top end came off and it’s no wonder it didn’t start. The rocker arms are destroyed, the cam shaft lobes are pooched. There was oil up there but not at those spots. When I removed rocker arm holder everything was covered in ground metal residue and all the channels and holes for oil were clogged with the same. Piston and cylinder look good and no movement on con rod. Will check ring clearances and hopefully just have to hone cylinder we will see. I wonder if my oil pump is buggered or was it enough just to have those passages clogged that stopped oil from getting there.

F309A2F3-643D-4D45-ACC1-6400E5689965.jpeg

966FF7B4-CD51-4E85-A294-2079B4E95306.jpeg

2826F3A9-EEC0-497C-B154-F82307D628E3.jpeg

Edited by Steve Wagner

Share this post


Link to post
Share on other sites
6 hours ago, slotracer577 said:

Anyone have part numbers for swapping over to Cdi?

You just have to buy a complete one on Ebay.  It's way cheaper.

Share this post


Link to post
Share on other sites
19 hours ago, Steve Wagner said:

This seems wrong. Manual says .15 to .3mm and this is about 5mm

 

Looks like you have a case of the wrong size rings for the bore size....................like std rings in say a 1mm oversize bore.  From the looks of the cam, the bearings in the head are probably ruined also requiring head replacement.  Pretty normal to find this kind of damage due to the neglect and abuse most motorcycles endure..................:excuseme:

Old School Al

Share this post


Link to post
Share on other sites

Cylinder and piston within spec but near limit, bought 1 oversized new rings and all but 1 ring was in spec so filed end. Crossed hatched so so not perfectly at 45 degrees but maybe 30 degrees. Put it together. Kicked over with compression tester and it’s not great.   120 psi. Should I expect it to get a good reading right away or does the engine have to go through it’s break in/ heat cycles before it will fully seal?

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:


×