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Discussion Starter · #1 ·
I have been jerking aorund with my 69 CB350 for a few weekends now. This bike was the best running bike I have had and after I got my CB450 I didnt ride it much last year. This year it is deciding to not want to rev through the gears, cuts out above 4500 to 5000 rpm. Erratic idle. Sluggish throttle response. I checked everything. Compression, points, timing, velves, plugs, I could go on but you get the picture. Last night while getting ready to do the compression test I smelled the gas coming out of the cylinder,,,,,,,,,, hmmmmm,,,, didnt smell too good.
I got to thinking. I did put Stabil in the gas but since I didnt ride it much last year that could be 2 year old gas in there. I think I will drain and replace it before I go any further.
Don
 

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Have you checked your petcock for proper operation? If not then I'd unhook the fuel lines and run them into a clear plastic container and leave them overnight. Taping off the container may help with any evaporation worries. If there's anything in the container then you know what needs fixed next..

GB :mrgreen:
 

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Discussion Starter · #3 ·
I rebuilt the petcock when I put this bike back together and I have checked to make sure that the gas is flowing. I had stripped the paint on this tank and before painting took it to a radiator shop and had it cleaned and sealed so I dont think there is any dirt coming out of it. I also checked the sediment bowl to verify that. All that being siad I still think I have a plugged carb. I put new gas in it and it still runs like the idle jets are plugged. I drained the bowls this winter thinking I would have clean jets this spring but the fact is that it still must have plugged jets. This bike is just getting back at me for letting it sit all last summer without riding it. It is PISSED !! I will take the carbs off this weekend and clean them up and I feel sure that will fix the problem and then ride the bike more often. I know it is rough duty but someone has to do it.
:p
Don
 

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"This bike is just getting back at me for letting it sit all last summer without riding it. It is PISSED !! "

Don...That's what happens when you ignore one female to play/be with another female....Talk to her...tell her the 450 was only a fling, and you still love her best!...LOL....
 

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Listen to Steve here with his "half his age wife" and mini choppers.. You old dog you.. :lol: A regular romeo we gots here.. :roll:

You're lucky I don't have access to change usernames Steve. ;) :p


Oh and Dslick, I meant checking the petcock to see if it flowed AFTER being shut off. Hence putting the lines into a clear container. To see if the crankcase was getting fuel into it.

My ritual for bike storage is to shut off the petcock and then run the bike until it dies. Thereby clearing all fuel from the carbs. No varnish/carb cleaning the following year.. Plus adding Stabil to an absolutely FULL tank. It prevents condensation in the tank. Come springtime, a quick oil change and turn on the fuel and I'm riding after checking the tire pressures!


GB :mrgreen:
 

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Discussion Starter · #6 ·
I didnt understand what you were suggesting with the petcock and that is a great idea. I take the drain screws out to drain the bowls but I do put them back in and what you are suggesting could happen. I checked the oil before I started it for the first time and it was acutally a little low.
I took the carbs apart tonight and was surprised to find some very fine crap in the bowls and some plugged jets. I also found that the float settings were a bit off. Funny how when you have a couple of bikes that you forget what you have done to which one. I would have sworn on a bible that I did those carbs but in fact it must have run ok when I got it and never took them apart.
It is raining here in Cincinnati so I couldnt ride it but it idles and revs perfect now. I cant wait for a dry day to run it down the road. I WILL ride it more this year. Maybe I can get Brown Bomber to help me get out more.
 

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Discussion Starter · #7 ·
****,,,,, it is better but not right. Back to cleaning the carbs again. Idles great, but comes off of idle and stumbles a bit and then breaks up at around 5,000 RPM. I set the float levels at 26mm. I put a timing light on it and the timing is right on and advances as it should.
Has to be carbs.
Suggestions?
Don
 

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Don.... What year is your 350? Correct float levels vary from 19 to 26mm depending on serial number... Are the jet tube O-rings new?( or old and nicked up?)....
I HATE to even mention it, but that does sound like it could be a pinholed diaphragm.... this often occurs just from setting.....
 

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Discussion Starter · #9 ·
I suspect the diaphragms now too. I never mess with those if the bike runs right for fear of tearing one. I may look at them the next time I get to work on it. The bike is a 69 and I checked the shop manual against the serial number ( I cant remember what it is now ) and I am confident that 26 is correct but at this stage I am going to check all my work again. Thanks. Don
 

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Discussion Starter · #10 ·
Got to work on the bike again tonight. Found a tear in one of the diaphragms. One seems to be in way better condition than the other so I think it was a replacement at some time in the life of this bike. This has to be my problem. Thanks for the help.
Don
 

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Discussion Starter · #11 ·
Has anyone ever used the diaphragms from Sirius Consolidated Inc that sells on Ebay?
 

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Discussion Starter · #13 ·
Thanks I will try that. I live in Cincinnati so I may try Western Hills Honda first and if they have them just pick them up. They arent usually the cheapest but I still try to buy as much as I can from them and they really do try to help me out because of it. I figure that in the long run with what I save in shipping and time looking it is worth it. Terry has gotten me out of quite a few jams on these old bikes on parts.
Don
 

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Your options are limited - those diaphragms have been NLA for a long time.
I doubt Western will be able to get them, but it's worth a try.
Be prepared to spend big bucks.......
 

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fasterspider said:
tbpmusic said:
those diaphragms have been NLA for a long time.
Bill, will the diaphragms from ebay work?

Item # 380121812179 on ebay
Ray -

I really couldn't say, I've never tried them.
The diaphragms are generally integral with the slides themselves, and sold as a unit.
I never really attempted to remove the old diaphragm from the slide and replace it.
With no 350 on hand, I can't offer anything here.........
 

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tbpmusic said:
fasterspider said:
tbpmusic said:
those diaphragms have been NLA for a long time.
Bill, will the diaphragms from ebay work?

Item # 380121812179 on ebay
Ray -

I really couldn't say, I've never tried them.
The diaphragms are generally integral with the slides themselves, and sold as a unit.
I never really attempted to remove the old diaphragm from the slide and replace it.
With no 350 on hand, I can't offer anything here.........
I have a pair of slides and a guy in New Zealand who wil sell the diaphragms to me a lot cheaper than Sirius will but, they are still expensive and I will have to wait for a sudden burst of cash to buy them.
 

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Discussion Starter · #18 ·
I just bought a set of the Sirius diaphragms and should get them in a couple of days. There is a procedure for fixing these things and I will be the test mule on this one for the list. Looks pretty straight forward but the only thing is that you have to cut the plastic ring that holds the diaphragm on and then glue it back together. As soon as I get them and give it a try I will post pictures and let everyone know how it went. This is an expensive experiment but well worht it if it works. The diaphragms were $94 shipped to my door.
Don
 

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Discussion Starter · #19 ·
Well, i got the SCI diaphragms and installed one of them on the piston that had the torn diaphragm. The original is held on with a plastic ring that fits into a groove. I have no idea how to get that plastic ring out without damaging it and I dont think that it could ever be reused. I tried a few different ways but ended up putting some Hylomar Universal Blue gasket maker on the diaphragm and using that to adhere the diaphragm to the piston. I then found an oring that fit in the groove that the plastic ring was in and that was a tight fit against the diaphragm. I let the assembly set for a while to let the adhesive cure and the whole thing turned out to work quite well. The proof would be if it would last while running the bike.
I put everything back together and it still didnt rev past 4500. I determined that it was running rich when cutting out with the choke test so,,,,,,,,,, off came the carbs again.
This time I took a closer look at the orings on the jets and decided to look in my left over carb parts inventory for orings to put on those. Found some and installed them and now the thing would hit redline if I wanted it to. The thing runs perfect now.
Turns out I had three problems, the plugged idle jets, the torn diaphragm, and the leaky jets seals which let too much fuel in on open throttle.
It always amazes me when these bikes prove to be so simple but take so long to figure out sometimes.
Diaphragms are expensive to fix but as we all know pretty much impossible to find so we are going to have to repair what we have and it looks like it is possible. I bet there are even better ways than I used but for now I am trying to keep this bike happy by riding it more often. Tough duty but someone has to do it.
Don
 
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