Honda Twins banner
1 - 6 of 6 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
I got this motorcycle from my fathers estate. It had sat for seven years but since it is a 1982 CB450 with 13000 miles on it I set out to fix it.
Here is what I have done 1)Headlight circuit cleaned all connections--now headlight works.
2)Cleaned carb in Napa gallon pail of carb cleaner, blew it out with compressed air.
3)Bought two o -rings I damaged doing 2--the boot to engine one and the small o ring on the side diaghram.
4) With carb back on there are no obvious vacuum leaks--determined by spraying starting fluid on the carb possible leak areas to see if idle speed changes... however.
It wanders like mad!!! Start it up on choke and it runs 2500 -3000rpm's. Drop it down too fast off choke and it kills.
But warm it up and it runs ok.
Seems the carb sync is a little off, but I have a homemade carb sync manometer with brake fluid in it next. For now the left is 2 inches and the right is 12 inches on the vacuum gauge. I cannot run the carb sync because it will suck it out of there!!!! I shut it off to prevent that!!
What is causing this unusual problem? I have the pistons inside that bring a rod up and down--CV carbs. I did a compression leakdown test and both cylinders/rings/valves are tight and hold 90 psi pretty good at tdc.
Can anyone help? Is it pretty certain that it is in the carbs?
BTW I ran this a week or two on errands and such--but started the carb cleaning after that as it seemed sluggish.

Sorry, I posted this on the DOHC site without realizing, mine is a SOHC. I have not even noticed the cam yet!
But,
 

·
Registered
Joined
·
489 Posts
I can't really help you with the carb problem besides to say to check the float heights. Seems your carbs are way out of sync. Try manually syncing them before using the manometer. I think there is a thread on here somewhere that describes the method.

However, I'm pretty sure this site is geared towards Honda Twins, meaning 2 cylinders. We don't much care how many cams you have....unless it is 3, then that would be interesting. ;)
 

·
Premium Member
Joined
·
1,612 Posts
karinier said:
Sorry, I posted this on the DOHC site without realizing, mine is a SOHC.
All fixed mate :cool:
Try adjusting the difference by feel before reconnecting the manometer, then be ready with the kill switch to see how close you got 'em. Allow the fluid to retract to level before trying again so that you dont suck that brake fluid into the carbs. Good luck.
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #4 ·
Thanks so much for the advice. It just seems it is right on the verge of really screaming. I used to drive a 12.75 sec 115mph quarter mile time 375 hp car, and this is going to be close to it. But not yet....
I bought a new gas cut off diaphragm for $31 and put it in last nite, since the old one looked gunky. So starting it up, it ran fine at first although idling high, so I went around the block, but by the time I got it in the garage it was as hot as a pistol and barely survived the trip without killing. What causes this? I am only happy that both cylinders are firing, as before the right side exhast pipe was cooler--so that I could put my hand on it. it appears that carb sync is the issue, so I will have to take the carbs out and set them manually close with a drill bit on the one side and check with same size on the other. Should I bring the pilot idle screws both back to normal---2 turns out?
This web site is fantastic for information!! :) Oh, by the way my starting button would not work last nite. I hope that is not worn out. Parts are so hard to find for my 82 Nighthawk. I will attempt to get thru these items tonite and this weekend!
 

·
Registered
Joined
·
636 Posts
i had the same thing with one exhaust being cold. blocked idle circuit in the carb. i would make sure all your tiny little ports and stuff are clean, otherwise all else is for nothing.
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #6 ·
This is helping a lot. I got it up to 60 on good power today and I had to adjust cloclwise about from 6:00 to 9:00 on that sync screw. I don't dare move it! It starts easily. I found that starting switch problem was I had it in first! :lol:
 
1 - 6 of 6 Posts
Top