Honda Twins banner

1 - 10 of 10 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter · #1 · (Edited)
I bought this bike from a guy who put it down 20 years ago and never touched it again. Over the last few months I've decided to make this bike my hobby and gone through the whole bike replacing every piece of plastic, rubber, or gasket. I'm so close to getting it idling but it just refuses to idle without just a little bit of choke, even after being plenty warm

I've cleaned both the carbs in chem dip for 24 hours each, rinse and blowed out with compressed air, I ran a wire through each one after that to make sure everything is clear. I've triple checked and cleaned all my jets.

Here is a video of it running and stalling with out choke.


Parts I've replaced:
Carbs:
Float gasket
Float
Float needle
Accelerator pump diaphragm and oring
Both the air valve diaphragms and orings (forgot what these are called)
And all the other plastic bits.

New oil and spark plugs. New air filter in the stock air-box.

I've replaced the intake boots and o-rings.

I've rebuilt the engine and replaced all the gaskets and piston rings, with no oil leaks with good compression.

I've checked for vacuum leaks around the boots and petcock but haven't found anything.

I bypassed the fuel valve and filled the carbs manually to see if they're just not getting enough fuel, no dice.

I might be missing something but I feel like I've tried everything, and it's driving me crazy. These carbs don't have adjustable floats, so even though the float is just out of spec I can't fix it. My older float needles sit right at 14mm and the new float needles sit a bit above 16mm and spec is 15.5mm.

I've tried adjusting the pilot screws all different ways. They're set to 3.5 turns out at the moment. Factory is something like 2 or 2.5 turns but when I got these carbs they were set to 3.5 turns. Plus I think the symptoms are bad enough that I don't think the pilot screws adjust enough to help. I've been turning them in and out and they don't really do anything noticeable.

Any advice or things to try would really help.
Thanks.
 

·
Registered
Joined
·
1,364 Posts
Here is a LONG SHOT... any chance of locating another set of (known) good carbs you can borrow? Slap them on.. see what's what? If your compression chamber is good.. the AIR to FUEL ratio factors start at the airfilter and end at the intake at the head...
I suggest starting at one end.. but it got a feeling your carbs may have either a clogged oraface, wrong jetting, or maybe a seal or 0-ring missing or worn...
What was the mileage? Was the bike cared for well? Left out in the elements? I have seen carb parts pitted and worn past a normal "rebuild" point and required remanufactueing (sleeves & bushings)..
I'm having a lean issue with my 65 S90.. I'm pretty sure I've got a clogged orraface somewhere..
 

·
Premium Member
Joined
·
10,203 Posts
What happens if you open the throttle while holding the choke open enough to keep it running?

Welcome to the group.

Got pictures?:p
 

·
Registered
Joined
·
805 Posts
One thing you don't mention having done is adjusting the idle with the knob between the carbs. Might be obvious but obvious is better than removing carbs.

If you're already doing that and it'll rev fine the carbs are probably dirty still unfortunately. Click "fuel supply and Carburation" at the top of this page and check out the rebuilding VB carbs sticky on the resulting page (pictures with text on page 11) to make sure you didn't miss anything.

Also are you 100% sure you've measured the floats correctly? Unless something was seriously wrong with your original float needles you should be getting the spec measurement. Non adjustable floats shouldn't just change height unless seriously messed with or wrong pins used etc.
Check out the pictures in the VB carb rebuilding sticky for the correct method
 

·
Registered
Joined
·
9,796 Posts
+1 on idle speed adjustment.
 
  • Like
Reactions: dmfcb750

·
Registered
Joined
·
5 Posts
Discussion Starter · #10 ·
One thing you don't mention having done is adjusting the idle with the knob between the carbs. Might be obvious but obvious is better than removing carbs.

If you're already doing that and it'll rev fine the carbs are probably dirty still unfortunately. Click "fuel supply and Carburation" at the top of this page and check out the rebuilding VB carbs sticky on the resulting page (pictures with text on page 11) to make sure you didn't miss anything.

Also are you 100% sure you've measured the floats correctly? Unless something was seriously wrong with your original float needles you should be getting the spec measurement. Non adjustable floats shouldn't just change height unless seriously messed with or wrong pins used etc.
Check out the pictures in the VB carb rebuilding sticky for the correct method
I think trying to increase the idle speed is a good idea. Also, what could, plugs and caps are you using?
Idle speed adjustment could definitely cause your symptoms and would be an easy fix.

View attachment 246529
+1 on idle speed adjustment.
Gotta agree with the idle adjustmen. Check the spevs for the correct setting. See if that works. Post results. Easiest fix first. Then, look at valve tolerances.

Sent from my SM-G920V using Tapatalk
BINGO BOYS. I'm a dummy, and you guys are heroes.


Also a note to anyone who's transmission refuses to get into gear from neutral after a total rebuild. Make sure you put the got-dang crush washer in before your neutral sensor. I tore the whole engine apart to fix my botched transmission to just realize that 1mm of clearance was blocking up my entire transmission.

Now I just have to fix my fuel valve so the On works instead of only reserve mode. And get some tires then I'm finally ready to ride it.
 
1 - 10 of 10 Posts
Top