Heats Up Then Runs Badly

[Lamaddict]

Well, I've changed the stator, coil and lead , petrol cap, plug (and reset it), HT cap, petrol pipe( it was rotting), cleaned the jets many times, choke was sticking but fixed that, cylinder head was a bit loose and I've had it off and retightened it, still the same!

14 miles to work, first 5 miles great revs great up to top speed etc, then about 6-7 miles it holds back a bit, 8-9 miles back fires at high revs, 10- 14 miles coughs and backfires as I try to rev away, all the way f..ing home. Once home is revs OK. Jump on it again when cool and it does exactly the same 'first 5 miles great.........

I'm sure the carb is OK but I might take out that ridge on the float bowl, I also resealed the tank but might replace the gas tap.

I thought it might have been the fuel but I don't think so.

[Solerunner1]

what does the plug look like if you pull over and shut it off quick when it's backfiring? It certainly sounds like it's overheating, running lean. Possibly ignition timing(checked with a strobe?), small air leak(at carb, intake manifold, or exhaust flange), try a cooler plug, blocked fuel tap.

I would try a cooler plug first, check to see if the tap is flowing enough fuel, and spray easy start/carb cleaner around all of the gaskets while it's running(if it changes the engine running, that's where your leak is) because they are the easiest.

[gavi4t]

just a daft one check if the breather hole in the fuel filler cap is not blocked

[lambrusco]

Had similar problems once. Turned out to be the rubber washer in the fastflow tap breaking down.

[camel]

re-sealed the tank.....what with?did you take the fuel tap off????

[Lamaddict]

re-sealed the tank.....what with?did you take the fuel tap off????

Resealed it with Kream believed to be better than Petseal also put a new tap on, took it out last night still the same runs great for a few miles then starts holding off etc. I'm going to have a look at the timing again, will strobe it. Also put in a new plug (B8ES) and set it.

[Lamaddict]

Re did the timing - still the same, check the cylinder head which was OK but when I took off the down pipe it was full of petrol????

[Tosh]

probably clutching at straws here but is it new/old petrol or have you tried some more but from a different supplier. also try the petrol handle on the arm mine was spinning and only let enough into the float bowl to go 1/4mile then conk out,while i was wondering what the prob was it filled up again so when i kicked it over we were of again for another 1/4 mile

[nelson pk]

Have you tried putting the choke on when its playing up to see if it runs better or worse?
If it runs better, its week and points to air leek or blockage. If it totally dies or makes the condition worse its overfuelling (choke slightly sticking or float valve sticking or worn) or maybe ignition.
May be worth sticking a multimeter on your stator when its warm to see if your coils are breaking down if your running an indian electronic when it heats up.....this is a common problem too.
If these tests dont show up the problem, borrow a cdi thats known to be working and try that.
You will always get dampness in the exhaust but if your getting a lot of fuel in there my personal opinion is overfuelling or your ignition isn't burning the fuel (missing a lot).
You need to narrow it down a bit with tests like these.
If you have stickys book it will tell you what the multimeter should read.
Hope this helps.

[coaster]

Looking at your first post, you mention changing everything in the ignition system except the CDI Maybe you forgot to mention it but if not, that should have been the first thing to check. Apart from that though, my money would be on the air leak theory or float valve adjustment.