C15 running issue

[B Murphy]

Great stuff, thanks Adrian

[johnan]

Re-reading your posts,B, it seems that your engine runs fine at speed , and the tickover is OK when cold but becomes erratic when the engine warms up.
That does sound like a carb. fault or an air leak when things expand with the heat...a coil breakdown would have been a possibility but you have eliminated that.
A bad electrical connection, made worse by temperature could be a culprit, maybe caused while fiddling with the leds.
Or the Boyer...but hopefully not!

[B Murphy]

Just an update - the new carb arrived today and installed it in 10 minutes. It still had a slight erratic tickover but not as bad as before and it keeps on running on tickover without stopping which is a big bonus. I took it through the lanes and it was really nice through the speed range. So I think it must be the Boyer. I also have another distributor that turned up today so I'll change it to points when I get chance. But to be honest the bike ran really well at speed (40mph) so I might just keep it as it is, at least it keeps running without conking out.

[chaz]

just a thought...head gasket? torqued down evenly or play in distributor or points shaft allowing it to float around therefore upsetting the Boyer?

[B Murphy]

Everything seems ok in that department Chaz.

Earlier I had one of those light bulb thoughts and might have solved it, I just need to put my thoughts into action if I'm correct.
I'm guessing that you all think that I have already tried what I'm about to say but haven't asked, probably my fault really for not saying.

I'm sat there thinking the only thing that I have wrong with the bike is the uneven tickover when it gets warm, all other ranges on the throttle are good.....so it has to be the Pilot (Johnan said probably carb fault). When I installed the new carb on saturday I had to unscrew the air mix screw approx another two times to get a jittery tickover (light bulb come on) I need to put a smaller pilot jet in to see what that does.

Is anybody with me on this or am I talking rubbish.

[chaz]

The pilot jet is the part which supplies most of the fuel at low throttle openings. It has a small hole in it which restricts fuel flow though it. Both the pilot air screw and pilot jet affects carburation from idle to around 1/4 throttle.

that said , I would have thought it would affect at both cold and warm, BUT, you say you have a new carb (Brand New?) , Im suspicious that if its still got the same problem then chances are its not that.

let me tell you a story. we went with our eldest to Gloucester to get him a Suzuki Bandit, his first 600. I rode it back home 50 miles, as far as the J17 M4 junction. He got on the bike and rode the 5 miles home. rode it into the garage and parked it. it stayed there for 3 months. It wouldnt start. we bought another loom, coils, cdi, plugs and kill switches but still no start. I had traced wires , nothing. Finally, I took it to a big dealer , after a week we called them, they had just sent it out on a test ride.
They had also traced the wiring....  we wouldnt have found the fault...there was a break in the wire near the ignition switch, when off the ends touched, when ignition turned on the broken ends repelled like a magnets. the ironic thing was, the second loom we bough (from a breakers) had exactly the same fault, presumably why the bike was broken.

It could be possible that the new carb has the same fault, machining swarf blocking a hole or jet.... maybe a time to go back to the start again.

[SUPERGRUMPS]

One thing nobodies mentioned is your tappet clearance, not enough clearance would mean the valves staying slightly open when the engine warms up. wont cost you anything to check 10thou for Ex and 8thou for inlet.

[B Murphy]

Well I sorted my running issue out. I installed a smaller pilot jet to 32 (was 35) and and larger main jet to 130 (was 100). It now starts very easy, ticks over without stopping and pulls through all the gears very good.

[AdrianS]

Glad you sorted it out!

[Blackthou]

Well done. only just seen and read through this post. Pilot jet or bit of dislodged swarf was my first thought.