Runnin on one cylinder

[Limegreen]

127ci Ultima, ultima single fire ignition'...

At very low rpm, just above idle it has been sputtering lately. At first I thought it was carb tuning issue ... so I just lived with it, but now i think it's ignition.

last time out I held it right at that rough spot at stop lights, etc. and I could pretty clearly here it going to one cylinder...and back...didnt sound like fuel issue to me. If I increase throttle at all it takes right off and sounds fine, runs good from there on.

So, it isnt much issue at all except in parking lots, etc. it can occasionally sound shitty. I am just worried itll get worse and eventually leave me stranded.

where shoudl I start?

I thought about messing with the carb (mikuni) but I know next to nothing about it and I really dont think thats it.

[RedWings]

I assume its the rear cylinder as usual. If so change the rear plug up to the next cooler plug.

[Limegreen]

hey thanks redwings

common, ey?

[Razorback]

If that don't do it look for manifold air leaks. First time I lost a cylinder with this new build it was a leak on the front cylinder. At idle she was missing bad once I was heading down the road with more throttle she wasn't bad. Last time I lost a cylinder just before I tore it down for paint it was coil related. I limped it home shut it down and that was it she would not fire on either. She did not run again until after paint and a new coil.

[Limegreen]

thanks razor

I went down from RN11YC4 to RN9YC and no change. Might try one more step.

[RedWings]

Will copper core plugs run on electronic ignition? I thought they had to be resistor type. I run r12yc's but I don't run electronics.

[Ricky-D]

Electronic ignitions have very specific needs regarding the components (plugs and wires) which, if ignored, will ultimately result in a lunched ignition module.

Seems to me, this could be the case with the ignition being discussed in this thread.

***

[Limegreen]

the RN11YC4 came in it from the builder, altho that dont mean a whole lot

except that he seems to get EVERYTHING from midwest, so it seems like it would be dialed

its got ultima plug wires, altho maybe there are many

[rem hamilton]

would check for the air leak at head, maybe ring gasket or mount bolts loose.
copper plugs have been used for electronic ign. for long time. if it cranks good cold and hot i would put the plug at the bottom of the list. carb. bolts good and tight?
if the carb needs adjusting go for it. satisfaction is better even if it's a couple weeks after screwing it up than having someone else do it for you!

[Limegreen]

Originally Posted by rem hamilton

would check for the air leak at head, maybe ring gasket or mount bolts loose.

thanks

copper plugs have been used for electronic ign. for long time.

ok

if it cranks good cold and hot i would put the plug at the bottom of the list.

yep it does

carb. bolts good and tight?

need to check

if the carb needs adjusting go for it. satisfaction is better even if it's a couple weeks after screwing it up than having someone else do it for you!

agree. started looking at the manual last night

thank you !!

[Batto]

Sounds like an air leak to me, start it up run it at the rpm that it faulters then spray some ether towards the intake's and carb, if it pick's up then you have a leak. mic carbs are easy to tune and set up, go to there site have a look very easy to understand. good luck mate.

[Limegreen]

Originally Posted by Batto

Sounds like an air leak to me, start it up run it at the rpm that it faulters then spray some ether towards the intake's and carb, if it pick's up then you have a leak. mic carbs are easy to tune and set up, go to there site have a look very easy to understand. good luck mate.

thanks

looks like you have a seriously fast heritage!!

[RB Donovan]

Originally Posted by Batto

Sounds like an air leak to me, start it up run it at the rpm that it faulters then spray some ether towards the intake's and carb, if it pick's up then you have a leak. mic carbs are easy to tune and set up, go to there site have a look very easy to understand. good luck mate.

Watch where you spray; If the carb even gets a sniff of ether near the mouth of it, it will pick up RPM.

I like carb cleaner myself. Not as explosive or dangerous as ether.

Any spray that is combustible will pick up RPM if there is a leak.
Non combustible liquid will drop the RPM.

[ewp1954]

2000i dyna did the same,rear cylinder was not firing,replace dyna 2000i and it was fine,also dirt in the tank will cause it to misfire if it cant get enough gas

[Limegreen]

Ordering new 2000i now