1986 XT600 running problem
 

Hi all.
I've got a 1986 XT600 43F.I rebuilt it 4 or 5 years ago,had no problems until last week.Bike stopped at the end of the road,pushed it home & started fault finding.NO SPARK:confused1:.
I have a spare pattern CDI so I plugged that in & got a spark,bike runs problem sorted. So I took it for a test run & about 60mph it's hunting,then it started doing loud backfires when I closed the throttle.I then tried keeping the rev's below 3000 RPM and when I close the throttle it's still backfiring..
I've got the bike back home & now I'm wondering if the fault is
a) a dodgy CDI unit?
b) something to do with the stator?
c) something else? Anyone have any ideas?
There's no sidestand or clutch switches so I can rule out those
thanks
MarkF

I would take out the carb and check/clean first, check wires on the bike.

I don't think it's the carb as it was running good until the CDI failed.
I bought the CDI a few years ago off here as a spare,
I'm not sure of the make but it says XT550/XT600 on it & looking on the web I've seen a photo of what appears to be the same unit on the Wemoto site.
I'm just wondering if I've got a problem with the stator.

If you pm me, I will guide you in checking your stator. I am currently assisting 2 others with the same problem. As these bikes age, this kind of stuff breaks. We can eliminate the stator with careful checks.

I await your PM, send me you email address too so we can correspond faster.

Steve

Steve I've just emailed you my address
Bike starts alright it just runs worse as the revs rise.
I'll get back to the problem solving later.
Seeing as it's late autumn over here I'm tempted to give the bike a full rewire over this winter
Mark

Could be carb or could be coil or pickup. No second advance would make it start fine and idle, then as the rpms clime it doesn't switch to the 36ish degree advance so it is running retarded. Tap the coil some with the bike idling and see if it changes how it is running, also see if it runs decent in higher rpms, right after you start it with a cold engine. The see if it get bad once everything is up to full temp.

In reading this thread, that has been my thought: electricity does funny things when the components, or the wiring loom, become hotter than their design range.

Donkey years ago I had a similar issue with an old Brit bike; eventually it turned out to be some component in the firing circuit (maybe the coil, but I really don't remember) which became faulty when it was even up to running temperature - the net symptoms were perplexing and frustrating.

well I did some tests & thought it was the CDI giving me trouble,so I ordered one from Borut at Zeeltronic.I fitted it saturday evening,ran the bike up,sounded good no problems.Yesterday I nipped out on the bike for a test run,everything's fine & as Steve Loomis reported in a earlier thread the bike feels stronger lower down the rev range :mchappy:.CDI was approx 200 euros + post.
Mark

Running problems with 1986 YAMAHA XT600
 

Hello folks, my mechanic cannot figure out the following problem:
my bike runs good, starts right away, idling is great, but at around 4000/5000 RPM it sputters like it's not getting enough gasoline flow. However the carb is great, cleaned several times. IS it possible that the CDI is defective? Even though it starts great? and again when you give gas and reach 5000RPM it starts "stuttering" and even for half a second like the bike is dead then continues running. Thx for your help!!!

Humm, you will have to go through the whole gamut of checking things. As mentioned above, possibly one of the trigger coils is not functioning. Do you have a manual? If so, check the ohms of the trigger coils, stator coils, coil primary and secondary. Check connections to the loom. Verify that the ground wire going to the coil area is definitely connected. It has been reported that an owner found the ground wire broken just inside the loom. He untaped the loom and traced the black wire inwards to the connection point in the loom and found it NOT connected. Check for corrosion on battery contacts and all bullet connectors to/from the CDI.

Other problems can be old and hard carb to head boots. They can leak air and run lean.

let us know what you find or need more info.