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Gidday Fellas,

Right this is where I'm at and sorry it's not a beemer thing but I'm going crazy!!

Son's 1986 Honda XR600, in good nick, a little rough here and there but is good fun for him.
It runs, starts and idles nicely, always has fresh oil and yes we look after it the best we know how to...

After about 15 minutes of running it starts to misfire badly, fart and lose power to a point of you cannot ride the thing properly and we have to limp back to the ute when we are up the bush and end our days fun.

I have cleaned the carbie many times, new plug, cleaned the air filter, checked for and no cracks in the air pipes that connect to the carbie, set the air/mix screw to the book specs, filed and buffed up the points...

I put another new plug in it the other day and yes it run nicely from idle when cold, then it done it again and started to misfire when really hot after about 15 minutes, I took the plug out and it was blackened up already, I run the standard plug and was wondering should I use a hotter number plug, would this help to fix the problem.......

We love to play around with this bike actually, but it is starting to give us the shits bigtime and I am refusing to take it to the bike shop as the bill will come back more than the bike is worth......It must be something simple!!!!!!!

Any thoughts here fellas........

You said "POINTS". that suggests a conventional ignition...?
First thing that comes to mind...Have you REPLACED the capacitor (condenser to some of you blokes!) the symptoms you describe is EXACTLY how the bike acts when the thing is no good AFTER it's subjected to some voltage. It sometimes works OK a bit after it "cools-off" but eventually, it'll leave you stranded.
Other thing is a bad coil, but change-out the capacitor first.
anyhow...You'll sure have a CLEAN carburetor...

PS. Don't even TRY to test it. It'll behave OK if it's not subject to voltage!!
About the same thought goes for the coil...only malfunctions when it gets hot.

Your symptoms are not exactly matching this, but is the tank venting? Is there a kink in the vent hose?

Gidday Fellas,

Jean: will try that first I think, sounds just like the symptoms....it warms up and then misfires...

Melville: tank is vented and no blockages, have crossed that one off my list awhile ago...

Right will ring the bike shop and ask a few prices.....Thanks heap

Sorry Fellas,

Major typo error.....My son does not have a XR600 He has a XR100

I have the XR600 which is running very nicely and throwing dirt everywhere....

Sorry bout that one.....New condenser $30.00 bucks and order from the dealer

I would do the typical ignition test of the color (colour for you) of spark and that will tell you if it is ignition. Then, only then go spending money. I would jump in any old condenser laying around for the test.

The coil is certainly a possibility. No testing them easily. Just R & R it.

Keep your money in your pocket.

Coil.

Hope the condenser takes care of it, but sounds like coil to me.

Major Softie wrote:Hope the condenser takes care of it, but sounds like coil to me.

Gidday Major,

Yes I hope so to, new condense is $30 which I ordered, the coil is $80.. I take the cheaper option first and see what happens, the little bike is 23 odd yrs old so replacing this and that as we go along will only be a good thing, I hope.