Misfire problems

[steve m]

Went out earlier to fill up with fuel for tomorrow, and ive got a misfire, from about 4k onwards

Its a tuned 1660 xflow, that has been running fine, nothing has been touched or changed since I last went out in it,

It no longer has a rev limiter fitted,
Misfire was before I filled up,
plugs and leads seem to be fine
dizzy cap seems to be fine, and not wet inside

would blocked jets cause a misfire ? as the electrical side all appears to be fine

steve

[DJ.]

If it is fine a lower revs, I had a similar problem with my old Elan. Changed the coil no difference, changed the HT leads and it cured it. I would think a blocked jet would cause problems lower down the rev range as well.

[andyf]

I once had a misfire that turned out to be the earth from the dizzy Base plate and the body. Only became a problem as the baseplate turned as it advanced the timing.

[steve m]

Thanks, I will have a look, at the leads, although they are new this year, and worked fine

will also check (again) the Dizzy connections

steve

[Matth93]

Have you got points/condenser on it still, I had a odd problem with the spartan before similar to what you have said and it was the condenser

[steve m]

Back home now, as it was getting worse, and driving on the M25/M4 would of been a nightmare

Its got an electronic system, so no points or condenser

The coil was hot, so I may have to change it, although that's only a year old

steve

[Tony C]

Steve,

I guess it could be the coil, but when mine packed up on the Sprite it gradually lost power, wouldn't rev, then stopped completely. If I let it cool down it would re-start and run 'til it got too hot again. Doesn't sound like your problem. I think ignition problems would show themselves throughout the rev range? Sounds like fuelling to me, blocked jet, blocked filter or the like. What carb are you running, does it have a second jet which comes into play at higher load?

Hope you get it fixed.

Tony

[steve m]

Tony,

I believe you are right, as ive cleaned out the jets on the carb 28/36 dcd TWIN CHOKE
and it appears to of sorted the problem

it does look as the second choke opens around 4k, and its emulsion tube appeared to be a bit gummed up

I may remove them again, and leave in a jar of thinners over night

steve

[Tony C]

Steve,

That's good news

When I logged in I half expected to see that the fault was down to the ignition and have to eat humble pie.

Hope to catch up for breakfast tomorrow.

Cheers

Tony