I bought my 1988 3CV FJ four years ago. It has 28k miles and although pretty it had had minimal maintenance.last year my carbs dumped petrol all over the hot exhaust. I stripped and ultrasonically cleaned them, fitted a full jet kit and set them back up. I. Installation they worked perfectly. Today I went out and got a low ram stutter....until about 2200 pm. It only became apparent when warm, not cold. Later on it seemed to get slightly higher up the revolution range, say up to 3k revs. After thatbit gies like steam.I kind of feel its electrical....but there's no science in that. My starting thoughts are coils and fuel pump. I cant believe my rebuild is faulty or clogged up again (nee fuel filter fitted). Any more knowledgeable thoughts would be appreciated. Rob
I should add starting is spot on, as is tickover.
Have you tried a new set of plugs? Could the plug caps be at fault? Maybe trim the ends of the plug leads for a good contact. Could one of the resistors in the caps have gone West maybe?
I had a similar fault on my XJR. Have you posted up on the UK FB page? Lot's of knowledge over there . https://www.facebook.com/groups/494216294033257
Sounds like your fuel/air mixture is set too rich. The raise in rpm's when the engine heats up is a telling clue.
Cold engines like to run rich, but when the heat up, the rpm's go up....
What are your main, Pilot and air bleed jet sizes? What needle clip position?
Checked your fuel level? The level in the float bowls may be too high causing a rich condition.
Thanks for the replies. I've never done faceache, so maybe I'll have to give it a try.
The jetting and needle position are factory standard. Float height was set and checked to factory spec. Factory air filter. The revs don't climb with the heat (I probably explained it poorly). The stutter appears when warm. The stutter has climbed from tickover up to (about) 2200 to about 3000 rpm before it clears (in gear and rolling) Tickover is rock solid @ 1000 rpm when warmed up, balance was good. Starting likewise good with no issues. The needles were set using the thumbnail method, which worked out at 2.5 turns on each needle.
I think I might replace all the HT leads and caps....they are 36 years old.....I can swap them across to new coils if it turns out they are duff.
It's not the plug wires. The oem FJ stainless steel stranded core silicone jacketed plug wires are damn near indestructible, amazingly robust.
Maybe one of the resistor plug caps is acting up, but the problem sounds like it's across the board, not just one cylinder.
My money is on the fuel side....not electrical side....unless you have mice, then all bets are off.
Although....I did have an intermittent high rpm stumble that drove me crazy...turns out it was a dirty run/stop switch on the handlebar. The 12v power for the ignition module flows thru this run/stop switch and this current was getting interrupted by dirty contacts....but only occasionally and at mid to high rpm.
I discovered this by running a temporary power wire from my battery to the ignition module, and the problem went away. I really don't like intermittent electrical gremlins..
Let us know what you find. Try to resist buying new electrical parts until you identify the problem.
That shit can get real expensive real quick.
Cheers
Pat
Thanks again for the reply. I'm not sure how much patience I have for this at the moment. Every time I fix something, something else breaks. I've just rebuilt the blue dots. Two of the pistons were jammed in and it took me half a day to get them out. I seem to always be fixing and rarely riding (and I like fixing stuff....normally)