Trouble starting XR 600

Just rebuilt my XR 600 and now having problems with hot starting it. Starting cold is no problem,Just one kick and it's running.Don't even need the choke.Once it gets warmed up no amount of kicking will start it.To start hot i have to turn the fuel,decompess it,5 or 6 slow kicks,release the decompress and kick.It will start then die turn the fuel on,kick and away she goes.It is obviously a fuel problem but have checked the jetting against the workshop manual and they are all standard,Float levels are right,new fuel needles,new slide needles and new o-rings in the manifold and still having the same problems.It's driving me nuts and makes it bloody hard if you stall out on a hill.Any help will be appreciated

Since it starts one kick cold and needs to be cleared out to start when hot, I would think that it is jetted too rich. A properly jetted 600R with stock carb should require choke to cold start and a brief warmup before the choke can be shut completely off.

I agree 100%. Too rich some how. Adjust it untill you need the choke when cold. Then try a hot start. Is this a xrR or a xrL 600? Maybe before the engine was rebuilt, carb had to be run rich to compensate other problems, & now all is right & thus carb is too rich?

Jetting is out. Did you do any mods to the engine? But its surely the jetting.

My bike is an '85 XR 600 R twin carb.Both carbs running a 122 main jet,slow jet is a 45 and the primary carb running the needle jet at the 4th groove and secondarycarb at the 2nd groove.Both float levels set at 18.0mm(0.71 inch).These settings and jet sizes taken from a Haynes manual.This bike used to start properly but developed these problems before the rebuild.No mods were done to the engine,rebuild consisted of new mains bearings,new conrod kit(std),trans mainshaft,3rd gear replaced,5th gear replaced,new gaskets and seals and new sprockets and chain.

I don't know about the hot cold thing, but. after i rebuilt my 86 this past summer it was hard to start. ended up being the automatic decompression cable a very little out of adjustment. readjusted both cables and valves. fixed it right up.

Another possibility.....

The 'ole 600's were known for hot start issues because of stator problems. Warm it up and take an electrical check of the stator windings. My '86 had this problem. Not sure what the specs are, maybe someone will chime in.

Good Luck-

Chad

Check your intake valve adjustment. You just rebuilt it, no jetting changes etc. Starts cold not hot is a classic too tight on the intakes. The best part is it wont cost you any money to check it out.

Did some more investigating and have discovered that the Timing chain needs replacing.Not sure if this could cause the problem or not.The chain seemed fine when putting the bike back together but before going on it's first ride the timing slipped and when i removed the rocker box i noticed that the chain was stiff and not sitting over the cog properly.

Those duals are known for leaky float needles. It really sounds like you're running fat. What does the plug look like? If the needles haven't been replaced in a while I'd look there first.

Did some more investigating and have discovered that the Timing chain needs replacing.Not sure if this could cause the problem or not.The chain seemed fine when putting the bike back together but before going on it's first ride the timing slipped and when i removed the rocker box i noticed that the chain was stiff and not sitting over the cog properly.

The tensioner can also go bad. Mine worked fine just sitting there with the head cover off. However, when running it let the chain get loose. My chain made all sorts of noise as is slapped around. Replaced the chain and the tensioner and that problem went away.

Replaced The Timing chain,reset the valves and she started on the choke.She even started once warmed up.Rode it steady through the gears,checked the oil,everything fine.Headed for the bush,got about 15 mins from home and all of a sudden big whirring noise from the motor and no compression,no phone signal so had to push it home.This happened today and i just couldn't be bothered with pulling the motor back down at the moment(i will do it through the week as to p***ed off with it at the moment).Keep you posted as to what happened.Thank you all for all your advice.

Here's the cause of the lack of compression

Buggered-3.jpg

Buggered-2.jpg

Buggered-1.jpg

Haven't gone any further than this ,saw that cog and nearly cried.

:lol: Man that sucks! Looks like you forgot to torque your cam gear bolts.

Great pics, but sorry to see the wreck. Maybe not as bad as you think. Get a new after market cam & gear.(probably new chain also) & check to see if valves got bent(piston may have hit when timing thrown off) Flush out metal shaving/pieces real good. Did it stop suddenly? If yes, you may have to check crank counterweights for shifting.(I'm not sure on this) Hope you getter back running soon without breaking your bank.

ouch!

Pulled the top end of yesterday and to my relief only things damaged was the top cog,bolts and chain.All the valves fine and sealing.There is one small chip on one of the cam lobes so will look at replacing or regrinding the cam(whichever is the less costly).

Have you figured out what caused this? Did the cam gear bolts loosen up? If it's just a small chip on the cam you could probably get away with just filing it down smooth on the edge of the chip.

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