CJ360T Great find, a fun ride!...NOT SO MUCH:(

[dawdish]

Hi all, I picked up this 360 about 6 months ago, it had been sitting, garaged for about 20 yrs, and it has about 7500 miles on it. The owner had put "stable" in the gas, so though the gas was bad, the tank cleaned out easily and the carbs were, generally, ok.
I rode the bike for about 2 weeks in stock form with no problems, then just befor I started the build, it started running crappy. I thought well Ill take care of that during the build. But today, though a little better, it still runs like crap.
The symptom is...it fuel fouls #2 cyl...not wet with fuel, but black soot, and of course then the plug starts cutting out.
The bike idles perfect...and before the plug fouls, it runs down the highway like a bat out of hell.
But at tip in, just off idle to maybe 1/8-1/4 throttle, it spits and sputters. Open the throttle further, and it will go ahead and run, unless its in too high a gear, then it gets worse.
The #1 plug is a nice brown color and has never fouled.
The carbs have been off and apart and adjusted numerous times. All jets and adjustments are "exactly" the same.
The compression, here @ 6K feet elevation is 110# on both cyl., (kick starter only).
What I've done...I cked the ignition system...no power loss to the coils, the spark pattern scopes out perfect side for side... but just for grins, I switched the coils side to side, with no change in the fouling. Last time I had the carbs apart, I found the sliders had turned on the diaphragms, fixed that, and now after a 30 mile ride, though it still spits and sputters @ tip in, it hasnt "totally" fouled the plug, though it is still very black.
Mods...Pod filters, supper trap, and the obvious "Cafe" stuff.
HELP! It's got to be ready for a 250 mile trip in 2 weeks... And thanks much!

 

[renslow]

What size jets are you running? She could be in the need of some fine tuning. Go ahead and re check the point gap+timing . Old bikes never leave you alone

 

[legendary_rider]

I wish I was experienced enough to help you out. I'm posting on here to wish you luck and follow your thread. Might help me someday!

 

[Sonreir]

Are those compression numbers after the engine has warmed up?

At 6000 ft, you should be getting no less than 130 PSI on a compression check with a warm engine.

Also... have you looked over the timing yet?

Finally, you will have problems getting it running perfectly. 360 carbs do not respond well to pod filters.

 

[my-79-750-k]

J-E-T-S... jets, jets, jets! Seriously, odds are your jets aren't tuned for the mods, and also, the pod filters, although it's been discussed to death, they just plain make it run like crap, and I have them on my bike. But, then again, I'm not at 6k ft either...

 

[dawdish]

@Sonreir... I'll reck the compression. when I cked it I was more concerned that it was even side to side, as my problem is only on #2 cyl.

@Jewbacca...Well Jewy (have mercy, I couldnt resist) I would expect it to be lean as well, as I have rejetted my other builds. Thats why I was surprised to find it rich on cyl #2. And with #1 mixture a near perfect tan brown on the plugI'm thinking I may not need to rejet.

But now let me throw a wrench...If #1 diaphram is leaking, that cyl would run lean...necessitating a wider throttle angle to compensate...causing #2 to run rich...maybe?

 

[Sonreir]

But now let me throw a wrench...If #1 diaphram is leaking, that cyl would run lean...necessitating a wider throttle angle to compensate...causing #2 to run rich...maybe?

Each diaphragm acts independently. So even if you did have to crack the throttle to compensate, the cylinder with the fully functional diaphragm would still read fine. The one with the damaged diaphragm would read lean.

 

[dawdish]

@Sonreir, that makes sense.

 

[dawdish]

Ok guys... After 80+/- miles since the last time I worked on the bike, here are pics of the plugs they are d8es.

Cked the compression this AM after the ride to work, both clydrs are 130#...perfect.

The bike is definitely running better...

 

[teazer]

D8 or B8? Pull the carb tops off and check the diaphragms and then pull the bowls off and set the float levels. While you have the carbs off, check all the air passages and jets.

 

[Sonreir]

B8ES on the 360s.

 

[teazer]

Thanks. I read the plug and wanted the OP to stop and notice the difference.

 

[CJHusband]

Forgive me for jacking the thread a moment, but what would be the acceptable range of compression be for a 360 at 150ft elevation? Really, at what point is a rebuild necessary?

 

[teazer]

I don't have the specs but I'd expect somewhere in the range 140-160 stock, 120-140 would run but lack punch, 100-120 flat, less than 100 barely able to get out of its own way. What does yours measure?

 

[habib]

I had a similar problem with my cb350, my compression was legit, carbs were clean, tuned, and synched but i couldn't get the left cylinder to stop carbon fouling. I have a bore-tech electronic ignition so i cheched timing with a strobe rather than static and it was off a bit. I also read, and heard that running BR8ES plugs would lessen the EFI and its effect on my electronic ignition. After adjusting timing and switching to plugs with resistors the bike is running perfect. I am sure the majority of the issue was timing but if you are running an electronic ignition maybe switch to plugs with resistors.

PS I am running the mikuni VM30's with K&N pod filters, they can be a pain to dial in but you can do it.

 

[CJHusband]

I don't have the specs but I'd expect somewhere in the range 140-160 stock, 120-140 would run but lack punch, 100-120 flat, less than 100 barely able to get out of its own way. What does yours measure?

I'm sitting at the high 140's on the build bike. The parts machine is in the 150's. So what I'm gonna take away from this is that I'm in good shape and haven't blown my budget. Thanks for the reply.

 

[dawdish]

I know its been a while, but I finally got back to the 360 tonight. Took the diaphragms out and thoroughly inspected them for holes or tears, nothing. Cked all the air bleed passages for...well anything...nothing. So I decided to do a test and see if switching sides with the diaphragms would switch the fouling problem over to #1 cyl.

In this process I noticed that the springs for the slides were different lengths. #2 spring was 1.5 inches shorter than #1, what the heck! Not knowing how long there supposed to be, I stretched the short one to match. Put her back together, and rode her home. It's SO much smoother, the loading up seem to be gone!

My thought is the short spring was allowing the #2 slide to lift too high, too quickly, causing a too rich condition on that cyl.

Going for a longer ride tomorrow and I'll ck the plugs after.

 

[teazer]

Nice catch. That's why I advocate stripping both carbs and putting the parts into two bowls and cleaning and comparing the parts. I find it easy to spot differences between two supposedly identical parts. It's almost impossible to tell if a part is the right size just by looking at it in isolation.

 

[legendary_rider]

Yay! Frickin awesome. Good catch.

 

[mikewerx]

Nice looking bike. I'll have to find you in Cortez next time I'm there... not too many CR's down in that town.