Honda Twins banner
1 - 10 of 10 Posts

·
Registered
Joined
·
47 Posts
Discussion Starter · #1 ·
image1.jpg

Hello everyone,

I have finally finished honing cylinders and lapping valves on my 75 cb500t, the bike looks great, but the carbs are junk. What I have done(to the engine).

-New rings
-Honed Cylinders (compressions good)
-New seals on top end
-New cam chain
-New Points
-Adjusted cam chain
-Adjusted tappets to .004
-Adjusted Timming (dead on currently)
-new seals and orings on carbs
-pod filters, I bought the wrong jets, so I will need to source the correct ones (and yes I am dead set on getting pod filters, I know, I know, haha)

Here are my current issues.

When I kick start it fires right up, well the left side cylinder starts and runs pretty well. no backfire runs smooth, right side wont fire, unless throttle is given then it will sometimes kick in and run. When I start turning the choke off the bike revs up really high. The mixture screw does nothing on either side. I tried to take the mixture screw out the left carb and the screw snapped, so I need to drill it out and find a replacement, will probably just do a full rebuild on both. Additional point, when I swapped the carbs, left carb on right cylinder, I experienced the same issue, right hand cylinder fired up and ran, left cylinder did nothing (other than rotate obviously).

I am thinking a full rebuild on the carbs is in order, looking for other things to look for while I wait for rebuild kit to arrive, hoping I can drill out the bad jet without doing damage. Any god sources for a decently priced set of 450 or 500t carbs? Thanks!

Pic for attention.
 

·
Registered
Joined
·
47 Posts
Discussion Starter · #2 ·
additional note: this is the same issue I was having before the top end rebuild, I thought low compression might be causing the issue, but compression is better on both cylinders, was slightly above 100 before rebuild now its hitting about 120 cold. keep in mind, I think the gauge I'm using is not incredibly accurate for this application, but I did get a compression increase, my dad used to use it on generators when he was a generator mechanic.
 

·
Registered
Joined
·
2,837 Posts
Sounds like your cables may not be in sync. I'd try to borrow a different tester and see what you get 120 is low. Did you mic the bores to see if they were in spec?
 

·
Registered
Joined
·
47 Posts
Discussion Starter · #4 ·
I bench synced the carbs, and when I turned choke off I made sure idle screws were both fully touching medal. The throttle cable is new also.

I did not measure bore, didn't have the tool, kind of kicking myself now, but I did get a compression increase and the lefthand cylinder is running well, right hand ran well also when I swapped the left hand carb onto it. I couldn't rev the bike because my cables were not attached when i swapped the carbs over, but it started right away and idled decently. I fiddled with everything for a full two days and the only adjustments that seamed to do anything to change it's wierdness were all carb related, which is why I'm thinking the main issues right now are carb related, but I am new to this type of maintenence so I could be wrong.

Before fiddling with everything when I backed the choke off it ran really well without reving out of control.. I don't know, I am trying to peice everything that has happened together, but nothing is coming together like it should, I did the full tune cam chain/tappets/timing a few times after messing with things to get it to run right and cleaned the carbs a few times, tried blocking the air cut off valves, sprayed wd40 all over the dang thing to look for vacum leaks, then I broke off the end of the mixture needle on my left hand carb, so now that needs a new one. haha...just so much. but with every adjustment to timing/tappets carb adjustments, the left hand cylinder ran (sometimes rougher, some times smoother) right hand cylinder wouldnt do much, but sometimes it would sputter and fire and run. with the left hand carb on that cylnder it ran, so I am thinking that carb needs a full rebuild with replacement parts and might as well do the left since i need a new mixture screw anyways.
 

·
Premium Member
Joined
·
10,203 Posts
Your rebuilding plan is a good place to start. You obviously have problems with at least one carb, might as well start with both fresh.

First advice I'd give is don't get an aftermarket carb kit. Most of the hard parts are unnecessary and often aren't correct for your application anyway. If you can, get a Honda gasket set (also referred to as a seal kit) and any specific hard parts you know you'll need. Individual jets are available at Jets-R-Us along with other sources.

While it refers to a somewhat different carb, this tutorial on carb re-building may be useful:

http://www.hondatwins.net/forums/63-fuel-supply-carburation/24191-rebuilding-vbulletin-carbs.html

And when you get it running, this may help to dial in the carbs to match your chosen intake/exhaust:

http://www.hondatwins.net/forums/63...4-cb400-cv-carbs-pods-how-make-them-work.html
 

·
Registered
Joined
·
47 Posts
Discussion Starter · #6 ·
Thank you for the advice, I will have to look into getting some individual parts. I did have some success today. I tore everything apart and adjusted tappets again, I was a bit off on the right cylinder I realized that I was not doing the adjustment right....dumb mistake. The right cylinder is now firing more normally. I also checked out the link about the pod filters, I moved the pod filters back a little as to not block air flow and this actual helped tremendously, I can actually rev the bike without dying, it's a major breakthrough. I'm still not out of the woods though. When I try to take the choke off the bike still revs out of control, what could this be?

Additionally, I can not get my clutch to work, freshly rebuilt, when i pull the lever the chock does not engage at all, I tried backing the to adjusters all the way out, nothing... I do have the little ball bearing in place, any ideas?
 

·
Registered
Joined
·
2,837 Posts
If the throttle plates are not closed far enough, when you open the choke too much air is allowed to flow causing high idle. That's why I think the cable sync is off. You can check by looking at them. A tiny sliver open.
 

·
Registered
Joined
·
47 Posts
Discussion Starter · #10 ·
Well, sure enough, I adjusted the idle screws and it worked like a charm. my sync was correct but I just had the idle screws to far in, which makes far to much sense and is something I should have thought about, haha. I was finally, for the first time since I bought the bike, able to ride it around the block. This bike is going to be a [email protected]#%@# beast... Definitely going to find some mufflers for it though, it's a little too loud and I live in a city, I don't wan't to piss all my neighbors off. It runs really rough and the clutch is pretty much non-operational, so there is work left to do.

The clutch plates are new so I will have to open it back up and make sure I did everything right. I had to adjust both barrel swivels all the way out and crank the adjuster on the case just to get the clutch to engage, when I pull the lever it's very hard to pull and my kickstart is not operational when the lever is pulled, does not seem right to me, not going to ride again until I have that figured out.
 
1 - 10 of 10 Posts
Top