Resend my activation email : Register : Log in 
BCF: Bike Chat Forums


Possible causes for no idle.

Reply to topic
Bike Chat Forums Index -> The Workshop Goto page Previous  1, 2
View previous topic : View next topic  
Author Message

Teflon-Mike
tl;dr



Joined: 01 Jun 2010
Karma :

PostPosted: 20:36 - 20 Sep 2017    Post subject: Reply with quote

Ow-kay.... dang suzuki's! GSX-twins has forked un-rocker and screw & lock-nuts then.. maybe...
Remains though, major service checks should be done and problems eliminated before final setting and fine-tune, like setting carb-balence and idle.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'
 Back to top
View user's profile Send private message Visit poster's website You must be logged in to rate posts

bypass2
Trackday Trickster



Joined: 12 Sep 2013
Karma :

PostPosted: 22:05 - 20 Sep 2017    Post subject: Reply with quote

are the vacuum port caps sealed no splits. what about the mixture screws what are they set at
 Back to top
View user's profile Send private message You must be logged in to rate posts

Sun Wukong
World Chat Champion



Joined: 02 Nov 2014
Karma :

PostPosted: 14:20 - 23 Sep 2017    Post subject: Reply with quote

Any final thoughts?
Check-

Carb body fuel lines + air lines.
Check vacuum hoses
Check carb rubbers
Float height

Any thing else that would cause it to stall when stationary and then take a period of time before willing to start again, when it will then start easily (about 30secs to 1min)

Cheers Mr. Green
____________________
Top cat
"Hard times lead to hard people. Hard people lead to good times. Good times lead to weak people. Weak people lead to hard times." Smegballs
"Oh and STE balloons would be one of the nicer things we would receive at the office, the amount of dog turd in jiffy bags is not funny." Jsmith86
 Back to top
View user's profile Send private message You must be logged in to rate posts

Robby
Dirty Old Man



Joined: 16 May 2002
Karma :

PostPosted: 22:05 - 24 Sep 2017    Post subject: Reply with quote

Give it a compression test.

I couldn't find anything that wrong in the carbs, apart from the heights being off and a little bit of dirt in the mixture circuit, and the balancing being off to a comedy amount. All thing that could make it misbehave a bit, but not fuck around to this degree - where it just will not idle.

Being a fairly basic air-cooled Japanese bike, I would expect it to still work fairly well with a lot more wrong with it. They aren't generally that fickle, a fuelling problem with this much effect should have an obvious cause. So I would stop looking at fuelling for now.

Compression test will give you an idea of whether you should be looking inside the engine. If it's way off, or way unbalanced, do the valve clearances then check compression again.

I didn't even start to look at electrical, for all I know this could be down to a couple of totally worn out spark plugs. Worth checking to see if you have a fat blue spark while you have the plugs out for a compression test. If the spark is fat and blue, don't spend any more time or money on electrical. This bike will run well enough on a weak yellow spark.
 Back to top
View user's profile Send private message You must be logged in to rate posts

Sun Wukong
World Chat Champion



Joined: 02 Nov 2014
Karma :

PostPosted: 18:29 - 25 Sep 2017    Post subject: Reply with quote

Will be compression testing her later on (fingers crossed Praying ), but still quite possibly an issue with the pilot air screw / jet.

We've been ferreting around and not found anything too obvious, however does any one know about the big brass blanking plates under the carbs?

I seem to recall something about drilling them off to get access to air screws?

That seems to be an unknown territory/unprobed area?

Any thoughts? Apparently it is a BSR 34 Mikuni carb.
____________________
Top cat
"Hard times lead to hard people. Hard people lead to good times. Good times lead to weak people. Weak people lead to hard times." Smegballs
"Oh and STE balloons would be one of the nicer things we would receive at the office, the amount of dog turd in jiffy bags is not funny." Jsmith86
 Back to top
View user's profile Send private message You must be logged in to rate posts

pompousporcup...
World Chat Champion



Joined: 15 Apr 2015
Karma :

PostPosted: 21:15 - 25 Sep 2017    Post subject: Reply with quote

yes, they hide the mixture adjustment screws which will either richen or lean out the idle/slow running mixture.. If they're blocked off then i'd assume they are set correctly already however they could be dirty or the the passages partially blocked from crap in the tank

Might explain why it runs on choke but dies the moment the choke is off (iirc) and also why it will run when you're on throttle as the fuel will be coming from a different circuit
 Back to top
View user's profile Send private message You must be logged in to rate posts

bypass2
Trackday Trickster



Joined: 12 Sep 2013
Karma :

PostPosted: 21:34 - 25 Sep 2017    Post subject: Reply with quote

the carbs on my bike does not have the blanking caps. what about if you lifted the slides/needle clip up one clip.
 Back to top
View user's profile Send private message You must be logged in to rate posts

temeluchus
World Chat Champion



Joined: 01 Oct 2008
Karma :

PostPosted: 00:01 - 26 Sep 2017    Post subject: Reply with quote

if the float needles are worn, or the o-rings around the seats are knackered you can get a very mild form of flooding that makes it run very rich at idle, causing stalling and unhappiness at low engine speeds.
____________________
Some shite cruiser. Now with guns and FREEDOM!
 Back to top
View user's profile Send private message Visit poster's website You must be logged in to rate posts

Kentol750
World Chat Champion



Joined: 24 May 2016
Karma :

PostPosted: 00:17 - 26 Sep 2017    Post subject: Reply with quote

Does it have a flat spot anywhere in the rev range when accelerating?
____________________
Some bikes.
 Back to top
View user's profile Send private message You must be logged in to rate posts

Sun Wukong
World Chat Champion



Joined: 02 Nov 2014
Karma :

PostPosted: 08:24 - 26 Sep 2017    Post subject: Reply with quote

We tried drilling them. It is not the usual thin brass plate. Luckily we stopped before we saw any airways. Seems the fuel mixture screw would have been blanked off originally (not now), but the air screw cannot be accessed Thinking

No obvious way to get them off, annoyingly.

I might swap the float needles around, just for funsies. See if that changes anything.

We did try raising and dropping the main jet needle, no obvious solution.

Bike will be for sale soon, hoping for 400-500 as a runner with mot and a fueling issue. In Manchester area now. Anybody wants a cheap project to annoy me with by getting it running beautifully, pm me.
____________________
Top cat
"Hard times lead to hard people. Hard people lead to good times. Good times lead to weak people. Weak people lead to hard times." Smegballs
"Oh and STE balloons would be one of the nicer things we would receive at the office, the amount of dog turd in jiffy bags is not funny." Jsmith86
 Back to top
View user's profile Send private message You must be logged in to rate posts

Robby
Dirty Old Man



Joined: 16 May 2002
Karma :

PostPosted: 08:32 - 27 Sep 2017    Post subject: Reply with quote

The mixture control/idle circuit screw is accessible. It's on the front of the carbs in the usual spot. It was fairly clean and the passageway was clear, I cleaned it up a little more.

Have you done any of the following yet:
- Compression test
- Valve clearance measurement
- Checked the spark plugs/spark strength

I don't think the problem is in the fuelling. Those carbs have been looked over several times by several different people. The problem has not got any better, or any worse. If the problem was in the carbs, then it would have either been fixed, or made worse by fiddling with a setting.

The bike is not that sensitive to fuelling. Sensitivity of that level is really something restricted to racing 2-strokes. A low power, air cooled 4 stroke is incredibly tolerant of poor fuelling. This is why people will complain of nothing more than a slightly rough idle when half the vacuum balancing plugs are missing and a bike is sucking in load of air, or why a CB250RS with a one inch split down the inlet rubber will just pop and bang a bit on deceleration.
 Back to top
View user's profile Send private message You must be logged in to rate posts

Sun Wukong
World Chat Champion



Joined: 02 Nov 2014
Karma :

PostPosted: 11:50 - 27 Sep 2017    Post subject: Reply with quote

Robby wrote:


The bike is not that sensitive to fuelling. Sensitivity of that level is really something restricted to racing 2-strokes. A low power, air cooled 4 stroke is incredibly tolerant of poor fuelling. This is why people will complain of nothing more than a slightly rough idle when half the vacuum balancing plugs are missing and a bike is sucking in load of air, or why a CB250RS with a one inch split down the inlet rubber will just pop and bang a bit on deceleration.


The smarter member of my current teams response.

Quote:
We can make it worse by fiddling with the settings easily enough. I have only found one solution to this specific group of symptoms on line. All other instances have no published solutions. NB: in the investigative stages, there are always suggestions for valve and compression testing. No published information on this being the problem, ever, anywhere, at all.


Solution being new carbs Laughing

Has had roughly the same fault for 2k. Sure it would have burnt through whichever part caused low compression by now?

Spark is strong, blue and beautiful. Still waiting on compression tester. Favours always happen slowly Confused
____________________
Top cat
"Hard times lead to hard people. Hard people lead to good times. Good times lead to weak people. Weak people lead to hard times." Smegballs
"Oh and STE balloons would be one of the nicer things we would receive at the office, the amount of dog turd in jiffy bags is not funny." Jsmith86
 Back to top
View user's profile Send private message You must be logged in to rate posts

Sun Wukong
World Chat Champion



Joined: 02 Nov 2014
Karma :

PostPosted: 18:52 - 27 Sep 2017    Post subject: Reply with quote

How about this.

https://gstwins.com/gsboard/index.php?topic=71048.msg853189#msg853189 tl;dr = O-rings behind mixture screws cause idle issues with gentle leaking.

We are off to investigate after dinner.
____________________
Top cat
"Hard times lead to hard people. Hard people lead to good times. Good times lead to weak people. Weak people lead to hard times." Smegballs
"Oh and STE balloons would be one of the nicer things we would receive at the office, the amount of dog turd in jiffy bags is not funny." Jsmith86
 Back to top
View user's profile Send private message You must be logged in to rate posts
Old Thread Alert!

The last post was made 6 years, 184 days ago. Instead of replying here, would creating a new thread be more useful?
  Display posts from previous:   
This page may contain affiliate links, which means we may earn a small commission if a visitor clicks through and makes a purchase. By clicking on an affiliate link, you accept that third-party cookies will be set.

Post new topic   Reply to topic    Bike Chat Forums Index -> The Workshop All times are GMT + 1 Hour
Goto page Previous  1, 2
Page 2 of 2

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum

Read the Terms of Use! - Powered by phpBB © phpBB Group
 

Debug Mode: ON - Server: birks (www) - Page Generation Time: 0.16 Sec - Server Load: 0.11 - MySQL Queries: 17 - Page Size: 82.85 Kb