Author Topic: CB350 Issues (Read 15513 times)

.RJ · « **on:** June 18, 2008, 06:42:39 AM »

I just picked up a CB350 in great shape - 8600 miles - and it started up and ran pretty good initially. I didnt ride it very far or hard before I bought it, but that was taken care of pretty quickly. I noticed at higher rpm (over 7k) the ignition would break up and then after riding for 20-30 minutes the floats would hang up and not let fuel into the bowls.

I tore down the carbs (diaphragms looked good), put new floats, seats and valves in, blew out the passages and put them back on the bike - they're definitely getting fuel now and the bike seemed to run pretty good in the garage and then I moved onto the ignition. New plugs and points put in and now the right cylinder wont fire - points are aftermarket and i set them to spec (.3-.4mm gap). I cant rule out still having a carb problem, but the float bowl is full of fuel.

Also, while it was sitting in the garage with the generator cover off (so I can turn over the engine and see the timing marks) it started puking oil out of the crankcase and on the floor... I dont think thats normal... it sat for a few days with the cover off and no drips.

Ideas? Coil gone bad?

Raul CB750K1 · « **Reply #1 on:** June 18, 2008, 09:39:41 AM »

Have you checked whether you have spark? I'm having issues with my CB350 carbs. For some reason, if the bike sits for some weeks, one of the carbs refuse to give fuel. There is spark, I remove the air filter and I can see the bell going up and down. I need to completely shut the intake with my hand so the cylinder sucks gas directly, and after some backfires, it starts firing.

Regarding the generator cover, without it it is quite normal that you have oil dripping. Depending on your oil level and the floor tilt. Other bikes have a different design, allowing to remove the cover and see the ignition marks with the engine running -strobe light-

.RJ · « **Reply #2 on:** June 18, 2008, 09:43:27 AM »

I just thought of something - when it was pouring oil out I had it parked on the side stand - I had always used the centerstand before...

The right side does not have spark at the plug, although it did before. I wonder if there's something up with the points I put in? I may try the original points and see if there's any change. I've heard these carbs can be a real pain too.

Brantley · « **Reply #3 on:** June 18, 2008, 11:36:50 PM »

Man I miss my 350G. That thing was a TANK. You said you replaced plugs and points, what about the plug caps? I know it's a pain in the arse to get the tank off with the crossover line and all, but make sure all yr coil connections are solid and no yellow or blue wire has a chance to ground (on the frame at the coils or leading out of the points cover).

.RJ · « **Reply #4 on:** June 19, 2008, 07:03:07 AM »

I havent changed the plug caps - I got home last night, fired it up and it seemed to run just fine, and then a while later tried it again and it would only run on the left cylinder

Then sometimes it would pop and sputter on the right side too

I think I'm going to test the coils and see what I get... or buy some Dyna replacements.

bryanj · « **Reply #5 on:** June 19, 2008, 09:39:00 AM »

Points are shorting out on the cover when you refit it at a guess----common problem, and yes oil will pour out if the cover is off

.RJ · « **Reply #6 on:** June 19, 2008, 09:43:31 AM »

Yesterday I ran it around without the points cover on it - just as bad as it was before. Strange....

The PO put a bit of electrical tape on the inside of the points cover too, maybe this has happened before with the bike.

Brantley · « **Reply #7 on:** June 19, 2008, 03:53:52 PM »

Plug caps are cheaper than coils

. Test yrs. Much over 5k omhs- time for new ones. Heat makes resistance, too.

mattcb350f · « **Reply #8 on:** June 19, 2008, 06:53:29 PM »

Here's a relative story about a misfit 360T I worked on once....

I did the damndist things, much like you've described. One day great spark on both then one, then both.

Then no spark.........then lots of spark.

I changed points, plugs etc,

Never did get it working right before the owner took it home to strip it for restoration but I was convinced it had to be the coil. I changed everything else

Maybe your coil is on the way out too?

Matt.

Raul CB750K1 · « **Reply #9 on:** June 20, 2008, 03:38:16 AM »

How could a coil be in the way out? They either work or not.

I would say corroded coil connectors-pitted/oiled points, or loose plug cap wire. The wire screws in the cap; check that it is tightly screwed all the way in.

Don't know the reason for the duct tape. the points cover is covered in the inside by some material that to my understanding is some kind of magnetic shield, to avoid radio interference. It should make no difference.

.RJ · « **Reply #10 on:** June 20, 2008, 06:15:03 AM »

Quote from: Raul CB750K1 on June 20, 2008, 03:38:16 AM

How could a coil be in the way out? They either work or not.

Do they have a habit of intermittent failure before they pack up and quit?

http://z1enterprises.com/detail.aspx?ID=3207

I may pick up a set, if nothing else than to get everything new and reliable - I'd like to start riding it to work every day.

Raul CB750K1 · « **Reply #11 on:** June 20, 2008, 06:49:30 AM »

A coil is a transformer. If the wire is broken, the coil is unuseable. It the wire is not broken, the coil works. If it fails, it doesn't give any warning.

Hardened high tension wire? Broken inner wire? I posted a thread in the "Tips and Tricks" abour renewing the HT lead in the CB350 coils.

mattcb350f · « **Reply #12 on:** June 20, 2008, 06:53:07 PM »

Quote from: Raul CB750K1 on June 20, 2008, 03:38:16 AM

How could a coil be in the way out? They either work or not.

You're probably right Raul. I have never conclusively verified that the problems with the coils I've changed in the past were the fault of the coil itself.

I suppose the problem could have been the high tension lead out of the coil or the input wires.

I did have one case on a Rotax Two-Stroke twin where I was chasing an ignition problem where the spark was at first weak, then strong and eventually stopped.... sort of.

In testing, the spark it would intermittently return which caused me no end of grief in tracing the problem. I would fiddle with something and then it would spark a few times so I would put it back together and try to start it. It wouldn't, so I pulled the plug and..... no spark again.

I replaced everything but the coil and still nothing but intermittent spark. Changed the coil and It fixed it.

But like I said, I never verified that the workings of the coil were at fault and it may have been some other component of the coil unit.

Matt.

detdrbuzzard · « **Reply #13 on:** June 21, 2008, 06:53:11 PM »

did you change the condenser wheh you changed the points?

.RJ · « **Reply #14 on:** June 23, 2008, 04:58:58 AM »

Quote from: detdrbuzzard on June 21, 2008, 06:53:11 PM

did you change the condenser wheh you changed the points?

Nope, havent gotten that far yet - back into it sometime this week though, I'll take a look.

JeyLux · « **Reply #15 on:** June 29, 2008, 07:37:04 PM »

I've having the exact same issue on my CL350.

intermittent spark on the left cylinder. New Denso points and plate, new plugs, new condenser. I am considering new coils, but not sure.

Looked though the wire system, but I don't see anything. Let me know what you turn up. I was thinking coils just don't "start" going bad , but ... not really sure what else it could be.

I should mention the intermittent spark follows the coil. swapped boots, and nothing, then swapped cylinders (and points wiring) and it followed.... so i can say 1 coil is bad...or rather, going bad. Or maybe a wire? But i can't replace the wire...

What coils do I buy? Dyna 3ohm?

.RJ · « **Reply #16 on:** June 30, 2008, 09:04:05 AM »

I scored a new set of coils on ebay - just waiting on them to come in.

JeyLux · « **Reply #17 on:** July 09, 2008, 02:43:40 PM »

Did they work out??

.RJ · « **Reply #18 on:** July 12, 2008, 08:11:52 PM »

Quote from: JeyLux on July 09, 2008, 02:43:40 PM

Did they work out??

Yep, worked great! I had made a mistake with the carbs, but once I got that sorted it fires on the first kick and runs great! New points, coils, plugs, points and carb clean - simple machine indeed.

Unfortunately on the test ride I got 1/4 mile up the road and the rear tire went flat

But its back together now and ready to go.

JeyLux · « **Reply #19 on:** July 13, 2008, 02:52:29 PM »

sweet, i ordered mine today.

hopefully it works out!

JeyLux · « **Reply #20 on:** July 21, 2008, 08:12:38 PM »

worked great! I put in a set of Dyna 3.0 ohm coils new plugs and wires..

fires up beautifully now, and runs great. I love it.

I wonder if it was just a wire issue or coil issue, but either way, it's great. I love it.

ohiocaferacer · « **Reply #21 on:** July 22, 2008, 04:52:19 AM »

Guys.....a common problem with the CB350 twins is the coil wire where it goes into the spark plug cap corrodes and the copper wire disintegrates. Easy fix.....is to unscrew the spark plug cap from the coil wire. Take wire cutters and cut the wire back about 1/4" into some fresh copper wire. Now thread the spark plug cap back on.

I've had several Hondas.....twins and inline fours with intermittent spark issues and once the coil wires are trimmed back.....issues go away.

Helo229 · « **Reply #22 on:** July 22, 2008, 06:15:15 PM »

I was under the impression that coils could fault simply by over-heating.

JeyLux · « **Reply #23 on:** July 22, 2008, 09:23:57 PM »

Quote from: ohiocaferacer on July 22, 2008, 04:52:19 AM

Guys.....a common problem with the CB350 twins is the coil wire where it goes into the spark plug cap corrodes and the copper wire disintegrates. Easy fix.....is to unscrew the spark plug cap from the coil wire. Take wire cutters and cut the wire back about 1/4" into some fresh copper wire. Now thread the spark plug cap back on.

I've had several Hondas.....twins and inline fours with intermittent spark issues and once the coil wires are trimmed back.....issues go away.

I would love to say that it had worked on mine, but i did this on both cylinders including new caps, and it offered no change.

.RJ · « **Reply #24 on:** August 15, 2008, 07:00:06 AM »

Bike died again. Got 1/2 mile up the road and then nothing. Wouldnt start, lights very dim - I think maybe the battery is toast

This one really seems to hate me

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Author Topic: CB350 Issues (Read 15513 times)