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1972 honda cb350 - EXPERT Advice needed

This is a discussion on 1972 honda cb350 - EXPERT Advice needed within the Vintage forums, part of the Types of Bikes category; hi im new to the forum and have heard amazing thing so i though id put some great minds to ...


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Old 04-03-2006   #1
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Default 1972 honda cb350 - EXPERT Advice needed

hi im new to the forum and have heard amazing thing so i though id put some great minds to the test.

i have 1972 honda cl350 15k miles
rebuilt carbs
checked all wiring
verified point gaps and spark plug gaps
clear inline fuel filters (no sediment i can see)
straight pipes no muffler right now
carbs are getting gas, and whole bike has power
when i kick it over maybe 1 out of ten times it will make a loud bang like a backfire but it only does it once

personal opinion is that its a carb issue, ignition coils seem fine if im getting spark? also gas is going into the carbs and nothings clogged up ive checked and rechecked and rebuilt. i have also set the breaker points to the appropriate time and gap as specified in clymer manual.
if this means anything i have spark even when the kill switch is in the off position.
any help would be greatly appreciated, im at wits end
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Old 04-03-2006   #2
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Default 1972 honda cb350 - EXPERT Advice needed

You shouldn't have any spark when the engine kill switch is off. Something is hangin' up in there or shorted out.

Does it start at all for one? It may be severly lean due to the fact it has open pipes. If it's timed right, the plugs,points,and condensers are new, and the carbs are right it shouldn't backfire. Make sure the point contacts are clean and oil free, run a piece of like thin cardboard like that's on a back of a tablet between them to clean them off.

When you check for spark is it a strong blue spark? If it is thats good unless the coils are crapping out after a couple sparks. Also make sure the right plug wire is running to the right plug, maybe switch them and see what happens.

Another thing you might want to check is valve adjustment. If the exaust valve is hangin' open a bit or is too tight it could make it backfire. They should be like .003" intakes and around .005" exausts cold.

Here is what I would do. Double check your ignition timing. Make sure you don't have the point wires mixed up and they are running to the right set of points if it has dual points. Check the valve adjustment to see if it's kosher.
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Old 04-04-2006   #3
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Default 1972 honda cb350 - EXPERT Advice needed

thankyou i finally have something to go on
strong blue spark
good point with the wires though, im going to check
i wish the gravity carbs had some kind of prime, i dont think closing the choke is enough to suck some gas into the engine.
also if this matters the points are original and they were rusty i just figured them mechanically fine since all they do is make an electrical contact upon eliptical movement, and since i timed them right with proper gap i was getting spark, i thought that was the end of it, should i replace them?
and one more thing i believe ive aswered my question on these 2, the headlight assembly is off that wouldnt keep it from starting would it? spark+gas=boom?
there is an overflow nipple on the bottom of the carb should i run a line from it to the road?
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Old 04-04-2006   #4
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Default 1972 honda cb350 - EXPERT Advice needed

CB750's usually on the right track...That backfire could be caused by an exhaust valve hanging open allowing fuel to seep into the pipe, this might build up and cause the occassional backfire... Just met a guy Saturday that has more than 20 vintage 350's in a storage trailer, even some 4-cylinder models, he sells parts cheap (has hundreds of old jap bikes) Steve Horton (717) 532-6147
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Old 04-05-2006   #5
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Default 1972 honda cb350 - EXPERT Advice needed

You can file points with a nail file to clean them up some but if you got the time might as well replace them.

The gas should flow into the carbs. There is a drain on the bottom of the float bowl. You can unscrew it to see if you got fuel to them. I would put a hose on the bottom of them just to be safe in case the floats should stick. That way there gas will go on to the ground not all over a hot engine.

The headlight being off shouldn't keep it from starting.

Maico I might be callin' that guy eventually:D
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Old 04-06-2006   #6
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Default 1972 honda cb350 - EXPERT Advice needed

He's down by Chambersburg...also has about 20 or so CB750's. His parts are cheap, I bought an old QA50 engine for $15 No side cover or carb and I got no use for it but it was just so darn cute:)
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Old 04-06-2006   #7
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Default 1972 honda cb350 - EXPERT Advice needed

A 72 wouldn't automatically turn on the headlight with the ignition, I think that was mandated in 1977?
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Old 04-07-2006   #8
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Default 1972 honda cb350 - EXPERT Advice needed

He's down by Chambersburg...also has about 20 or so CB750's. His parts are cheap, I bought an old QA50 engine for $15 No side cover or carb and I got no use for it but it was just so darn cute:)

Any CB450 stuff?
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Old 04-07-2006   #9
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Default 1972 honda cb350 - EXPERT Advice needed

Yeah Uesque he had some of those but not as many as 350 & 750 also had most other size Hondas Yamahas and Kawasakis, some Suzukis. The guy has a dozen or so forty foot trailers packed full and lots settin outside.
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Old 04-08-2006   #10
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Default 1972 honda cb350 - EXPERT Advice needed

will cb350 run with straight pipes
i saw on the internet somewhere that it wont even idle if there is a hole in the muffler.
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