Honda Twins banner

1 - 20 of 30 Posts

·
Registered
Joined
·
34 Posts
Discussion Starter · #1 ·
After fixing my no spark issue I have come into an issue with my bike not holding an idle. I recently rebuilt the carbs with new kits, adjusted the floats to the proper 21mm. I can get the bike to start by holding the throttle open but once I let off the throttle it just dies, every time. I have adjusted the mixture and throttle stop screws, Throttle stop: 1.5 turns, 2 turns, 3 turns out, all the way in. Nothing is making a change, the slides are in properly with reapect to each side. It slowly revs up to 3k rpm amd stays there, once I even thinknof letting off the throttle the bike just dies. Any ideas?
 

·
Registered
Joined
·
13,085 Posts
When you fixed the no spark issue, did you set the points and timing? Retarded timing will contribute to a no idle problem
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #3 ·
Well, thats a good question, because i had set the timing with old points so perhaps I should go back through. Now, setting the timing on this bike the F mark must be at the timing mark just as the points begin to open correct? Thats how I did it previously. There are two marks one has no label and the other is the F, which would be 35-40 degrees out correct?
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #5 ·
Ok, per steves suggestion, I have done the following; fixed the the stuck advance mechanism, reset the timing, removed orings on carbs and made paper gaskets, made sure slides are not reversed, float levels set properly. I cannot get this bike to idle below 2500rpms. I can start the bike with throttle wide open, if I let off the throttle at all it slowly just dies. It will not idle after all of these suggestions/fixes. I just dont know what else the issue could be?
 

·
Premium Member
Joined
·
3,006 Posts
Blocked or partially blocked idle circuit in carbs ? If the mixture screws have no effect, this is a possible cause.
 
  • Like
Reactions: Rizingson and Simo

·
Registered
Joined
·
34 Posts
Discussion Starter · #7 ·
Pulled carbs apart again and all circuits are clear and clean. I also figured it may be a vaccum leak somewhere, so I used sections of an innertube and stretched those over every flange on the carbs it is still dying at idle. Gapped the points, made sure timing is spot on. At a loss.
 

·
Registered
Joined
·
4,770 Posts
How did you clean the idle circuit? It is notoriously hard to clean, it's separate from all the other jets ( there are 3 in your carb but only 2 are changeable) there's no line of sight so you can't see daylight from one end to the other. Are the slides in sync? What are the needles set at ? And what baseline are you useing fore the set screws?
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #9 ·
I used an air compressor, removed air screw and spring, pilot jet and there is air coming from all three orifices. My slides may be off I actually havent checked them, I have screens on my intakes of carbs so its tough to see in them but I will try. The air screw is set at 7/8 out and the throttle screw is set to 1 1/2 out. My needles I believe are set to center position.
 

·
Registered
Joined
·
805 Posts
I have screens on my intakes of carbs so its tough to see in them but I will try
Does this mean you've got non stock air filters? Also if you've got new throttle cables or routed too tight it's possible they'd be too short, pulling your slides up a little when they seem closed.
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #11 ·
Adjusted the slides to proper position both sides. Mixture screw one turn out, throttle screw about one and half.Started the bike, it starts up no throttle,sits at 2k rpms then about 30 secs later it revs and revs up to 6k and keeps climbing up until i hit the kill switch to turn it off, never touched the throttle once.
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #12 ·
I have NOS filters, they are the oval style. The cable is the original, not a replacement. The slides are definitely bottomed out. I have even sealed the seams on the insulators on the block with ultra black to insure there is no vacuum leak there too. This has to be carb related, everything else on the bike is to spec.
 

·
Premium Member
Joined
·
3,006 Posts
Started the bike, it starts up no throttle,sits at 2k rpms then about 30 secs later it revs and revs up to 6k and keeps climbing up until i hit the kill switch to turn it off
Have you tried disconnecting the throttle cables completely, so that the slides bottom out completely, then started the bike ? If it still revs to 6k then, that would rule out an issue with the throttle cable lifting the slides slightly, which is what I wonder is happening.

I speak from experience, it doesn't take much pull on the cables to have the engine screaming its head off with no load on it.

BTW, your choke mechanism appears to be badly bent.
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #15 ·
Yes, I see what you are saying about the choke mechanism I will try and bend it back up and certainly try the disconnecting the cables.
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #16 ·
I have bent the mechanism straight up on both sides now the mechanism works much smoother. As far as the slides, I completely disconnected both cables from the slides and the bike will not start. I covered the tops of the carbs to make sure no vacuum was occuring there. I reattached the cables on the slides and the only was the bike will start is if I open the throttle up. If I let the bike go anything below 2k it just dies immediately, every time.
 

·
Registered
Joined
·
4,770 Posts
Normally an engine starting and racing to 6-7k would indicate the slides are reversed in the carbs but they look correct from the photo. Can you confirm the slide cut aways are facing the airbox ( left slide will fit in the right carb if it's facing the wrong way and vice versa)As Richard asked what affect do the set screws have on the idle .
The screws have a baseline which you've already set but they need to be adjusted to bring the idle to 1200rpm
 

·
Registered
Joined
·
34 Posts
Discussion Starter · #19 ·
Both slides are indeed in correctly, thats one of the first things I check everytime I put the slides in. It is difficult to tell with the screws, I have a baseline of 1 turn out on the air screw and the throttle screw I am now leaving all the way out, or loose per steves suggestion on tuning, also to ensure the slides will bottom completely. I have even switched to an aux tank to explore whether its my tank/gas that is causing this issue. That seems to have no affect either.
 

·
Premium Member
Joined
·
3,006 Posts
If you had the throttle stops screwed all the way out, with the throttle cables disconnected, then of course it wouldn't start.

Air screws should be 1 1/4 ( one and a quarter ) turns out as an initial setting. Screw the throttle stops in until the slides just lift, it should then start with the throttle cables disconnected, idle speed being adjusted on the throttle stop screws then.

I'm suggesting doing it this way so that we can rule out ( or in ) a tight throttle cable being the reason for the jump to 6K.
 
1 - 20 of 30 Posts
Top