All Possibilities of hanging high idle

[timebombprod]

Okay so, I just need to know all the possibilities of having a high idle after giving the bike a little throttle, high idle being over 3000rpm, and only occurs when given enough throttle to reach a bit over 2000rpm. I can pull the choke rack to knock the idle back down to normal, but sometimes it will just go back up.

I have checked the intake boots for vacuum leaks and everything seems to be okay. I have disconnected the throttle cable and revved the bike by the carbs throttle and the throttle cable isnt the issue.

What else could it be? Video for reference.

https://youtu.be/1qEZNfiQbUc

I'm gonna have to mess with my fuel mixture screws as the sparks are covered in soot but all 4 do spark, so I'm gonna be adjusting by half a turn each time. They are champion plugs that are cross referenced from the ngk d8ea.

 

[timebombprod]

I do have a set of airpods I can put on the bike to see if its a vacuum leak from the airbox but I didnt want to risk overheating the bike from running lean, would this be okay to do just to test out seeing for airbox leaks?

 

[zed1015]

Hi, Ian.
Hope you were happy with the plungers.
Don't fit the pods. That will screw up the carburation on CV'S big time. Even with a jet kit and dual pods they never run perfect..
It does sound like a lean condition if opening the choke ( enrichener) steadies the revs.
It's very difficult diagnosing online but there's varying conditions that will cause the hanging idle and throttle cables and plunger seals which you have eliminated are two of them.
Air leaks on the intake boots, air leaks on the vac port covers, loose jets, sticking mechanical timing advancer and diaphragm leaks etc are the other usual suspects, even the cam timing a tooth out or restricted fuel supply ( partially blocked fuel filter) can cause this.
All i can say is work methodically , starting with the fuel supply at the tap and work through the system to eliminate each area.
You will eventually find the cause if you follow an organised path.

 

[timebombprod]

Hi, Ian.
Hope you were happy with the plungers.
Don't fit the pods. That will screw up the carburation on CV'S big time. Even with a jet kit and dual pods they never run perfect..
It does sound like a lean condition if opening the choke ( enrichener) steadies the revs.
It's very difficult diagnosing online but there's varying conditions that will cause the hanging idle and throttle cables and plunger seals which you have eliminated are two of them.
Air leaks on the intake boots, air leaks on the vac port covers, loose jets, sticking mechanical timing advancer and diaphragm leaks etc are the other usual suspects, even the cam timing a tooth out or restricted fuel supply ( partially blocked fuel filter) can cause this.
All i can say is work methodically , starting with the fuel supply at the tap and work through the system to eliminate each area.
You will eventually find the cause if you follow an organised path.

What's the vac port cover?

All I've noticed is over time this problem has got increasingly worse, it used to sit at 2k, now almost 4k. Only seems to happen when the bikes warm but that could be wrong.

I dont run a fuel filter it's just a fuel line.

Gonna probably have to check the cam timing just to make sure, but also that mechanical advancement.


Oh and the plungers work great now, just wish everything else did!

 

[Redman]

You say you checked for intake air leaks, I assume you mean the boots themselves are not cracked along thier body.

Other things to concider:
- boots old and stiff so dont seal well. boots old and stiff so the clamps have been overtightened and stretched out, and/or the boots deformed.

- boots separating from the base flange.

- boot o-rings old and hard. (orings up against the head)

- (and what got me: ) O-Rings in the enricher(choke) mechanism. HAve to completely break down carbs from the rack to replace these.

 

[zed1015]

On each carb there is a rubber cap that slips on and seals the ports that are used to attach vacuum gauges for balancing the carbs.
They are on the top of the carb at the boot side and on CV's usually have a squared off top .
This port is a direct link to the venturi so a leak there is the same as a boot leak with air being drawn direct into the engine.

 

[timebombprod]

On each carb there is a rubber cap that slips on and seals the ports that are used to attach vacuum gauges for balancing the carbs.
They are on the top of the carb at the boot side and on CV's usually have a squared off top .
This port is a direct link to the venturi so a leak there is the same as a boot leak with air being drawn direct into the engine.

I never knew about this, I thought the intake boots have those pieces for the carb syncing.

 

[timebombprod]

You say you checked for intake air leaks, I assume you mean the boots themselves are not cracked along thier body.

Other things to concider:
- boots old and stiff so dont seal well. boots old and stiff so the clamps have been overtightened and stretched out, and/or the boots deformed.

- boots separating from the base flange.

- boot o-rings old and hard. (orings up against the head)

- (and what got me: ) O-Rings in the enricher(choke) mechanism. HAve to completely break down carbs from the rack to replace these.

I changed the o-rings on the boots, and sprayed were they connect to the head, guess I'm gonna have to do a more in depth inspection. They didnt seem stiff but the clamps do seem a bit stretched. The carbs are a hard fit onto the boots but the clamps themselves do seem a bit worn

Probably gonna get at it tonight.

 

[timebombprod]

Plugs at idle speed, should I start messing with fuel mixture screws or is this considered okay, I dont think it is but making sure

 

[timebombprod]

Hey could you possibly tell me where the vac plugs are supposed to be, heres a picture of the carbs. Gonna replace the enrichener o rings.

For the choke, I noticed when I pull the rack out and let it back in I can hear air passing through

 

[timebombprod]

Also found this and nothing is screwed into it on any of the carbs, only one hole shows threading, should I be worried about this? It's only threaded on carb 3

 

[Big T]

On each carb there is a rubber cap that slips on and seals the ports that are used to attach vacuum gauges for balancing the carbs.
They are on the top of the carb at the boot side and on CV's usually have a squared off top .
This port is a direct link to the venturi so a leak there is the same as a boot leak with air being drawn direct into the engine.

I don't have a 650 on hand to confirm, but, from looking at the parts fiche, the sync ports are in the cylinder head and sealed with a bolt and washer

 

[timebombprod]

I don't have a 650 on hand to confirm, but, from looking at the parts fiche, the sync ports are in the cylinder head and sealed with a bolt and washer

It's in the intake boots, one is missing a washer, gonna just replace them with o-rings for now and see if I can just find the washer around here. The carb tuner has o-rings on the fittings so it doesnt seem like a bad temporary replacement.

 

[timebombprod]

Heres a video of tonight, explains what I've done and also shows the condition of my intake boots, and an idea im thinking of doing instead of buying new boots right away. Please watch!

https://youtu.be/TroCXtyPapc

 

[zed1015]

Hey could you possibly tell me where the vac plugs are supposed to be, heres a picture of the carbs. Gonna replace the enrichener o rings.

For the choke, I noticed when I pull the rack out and let it back in I can hear air passing through.


View attachment 62476

Hi, Ian. As already confirmed , those carbs don't have the vac ports on the bodies.
Some do, some don't depending on model.
The suggestion was only to ensure it was something you hadn't missed.
If that thread is a blind hole it is of no concern.
These carbs will have been used on several different machines and various drillings and mounts may not be used depending on application.
As for the choke, with the bike running it's normal to hear a hiss as the plunger shuts off the passage to the venturi if you listen carefully.
With the new seats those plungers are guaranteed not to be passing fuel in the closed position.

 

[tom203]

You got new boot o-rings, new choke plungers....I?m blaming the carb boots Or their clamps as redman suggested ,especially since you say hanging idle is getting worse.
spring for the oem boots or be adventurous and try a $30 set

 

[timebombprod]

You got new boot o-rings, new choke plungers....I?m blaming the carb boots Or their clamps as redman suggested ,especially since you say hanging idle is getting worse.
spring for the oem boots or be adventurous and try a $30 set

I uh, did something with the boots lol, if you watched the vid you'll know.

Gonna look and see if I have extra clamps and chose the best one, but if they're all pretty worn it's time to order parts.

 

[timebombprod]

As for the choke, with the bike running it's normal to hear a hiss as the plunger shuts off the passage to the venturi if you listen carefully.
With the new seats those plungers are guaranteed not to be passing fuel in the closed position.

Okay good just making sure, didnt know if its supposed to be like airtight where the o-rings and the visible rubber piece are, the brass bolt that threads.

 

[timebombprod]

What is this spring? Never noticed it before. I'm guessing it's meant to be there but at first I thought there was some metal shaving in my engine.

 

[timebombprod]

Hi, Ian.
Hope you were happy with the plungers.
Don't fit the pods. That will screw up the carburation on CV'S big time. Even with a jet kit and dual pods they never run perfect..
It does sound like a lean condition if opening the choke ( enrichener) steadies the revs.
It's very difficult diagnosing online but there's varying conditions that will cause the hanging idle and throttle cables and plunger seals which you have eliminated are two of them.
Air leaks on the intake boots, air leaks on the vac port covers, loose jets, sticking mechanical timing advancer and diaphragm leaks etc are the other usual suspects, even the cam timing a tooth out or restricted fuel supply ( partially blocked fuel filter) can cause this.
All i can say is work methodically , starting with the fuel supply at the tap and work through the system to eliminate each area.
You will eventually find the cause if you follow an organised path.

Using this to keep a checklist, got the throttle cable, plungers, the diaphragms, and now timing advance checked, and I did a little work on the intake boots so possibly getting that one checked, gonna get new clamps for the boots because these are probably worn.