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GSX600F - needs lots of choke until warm.

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ThatDippyTwat
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PostPosted: 19:11 - 16 Feb 2020    Post subject: GSX600F - needs lots of choke until warm. Reply with quote
So, '98 GSX600F. Needs a fuckton of choke and held around 3-4K until properly warm - 5-10 mins.

I thought it was inlet rubbers leaking, but squirting brake cleaner around the rubbers while it was running didn't make it rev at all. Which is a pain as I have a set of inlet rubbers here.

So, I'm at a bit of a loss. Once it's warmed up, it runs as you would expect any IL4 600 to, and starts back up instantly if still warm/hot.
Ideas appreciated.
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redeem ouzzer
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PostPosted: 19:43 - 16 Feb 2020    Post subject: Reply with quote
Blockage in the carbs or possibly a bit lean at the bottom end?
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jaffa90
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PostPosted: 21:24 - 16 Feb 2020    Post subject: Reply with quote
As said, the choke or starter jets sound ok but the pilot jets are lean.
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ThatDippyTwat
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PostPosted: 21:40 - 16 Feb 2020    Post subject: Reply with quote
Guess I'm cleaning carbs when I get a break in the weather. Cheers.
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Tankie
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PostPosted: 03:10 - 17 Feb 2020    Post subject: Reply with quote
Just screw in the pilot air screws a 1/4 turn, if they will move.
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redeem ouzzer
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PostPosted: 06:17 - 17 Feb 2020    Post subject: Reply with quote
Tankie wrote:
Just screw in the pilot air screws a 1/4 turn, if they will move.


If these are Mikuni carbs They are not “air screws”, they are mixture screws and control the fuel bleed into the pilot circuit, not the air. OP needs to back them out to richen it up.
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ThatDippyTwat
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PostPosted: 20:02 - 17 Feb 2020    Post subject: Reply with quote
Chatting with a previous owner (Friend of a friend) has turned up a few things.

Carbs were cleaned and balanced in October, by a reputable garage. They said it was inlet rubbers. Many receipts for this and other work and every single MOT sheet it's has are now in my possession.

It's a US Model (confirmed by engine number and the Haynes manual)- Air/Mixture screw is pre-set and non-adjustable.

I'll replace the intake rubbers - if this sorts it, it looks like I stumbled on a screaming bargain, it's had a fair few quid thrown at it and I didn't pay much for it.
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Bhud
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PostPosted: 20:31 - 17 Feb 2020    Post subject: Reply with quote
ThatDippyTwat wrote:


It's a US Model (confirmed by engine number and the Haynes manual)- Air/Mixture screw is pre-set and non-adjustable


I'm not familiar with that bike, but, going by what they did with Yamahas from that period (sold in the US vs sold in EU), there might be tabs over the mixture screws, to comply with California emissions (factory would have set them very lean) and anti-tamper laws. If you can drill them out, you'll be able to access the mixture screws and adjust them. Worth looking into this.
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jaffa90
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PostPosted: 20:55 - 17 Feb 2020    Post subject: Reply with quote
Bhud wrote:
ThatDippyTwat wrote:


It's a US Model (confirmed by engine number and the Haynes manual)- Air/Mixture screw is pre-set and non-adjustable


I'm not familiar with that bike, but, going by what they did with Yamahas from that period (sold in the US vs sold in EU), there might be tabs over the mixture screws, to comply with California emissions (factory would have set them very lean) and anti-tamper laws. If you can drill them out, you'll be able to access the mixture screws and adjust them. Worth looking into this.

As said,
https://www.youtube.com/watch?v=wAXcksgvDkM
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ThatDippyTwat
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PostPosted: 17:05 - 22 Feb 2020    Post subject: Reply with quote
Not had chance with all the storms.

However, a few people have suggested the valve clearances may be tight. Reason being she won't drop revs as quickly as she should, even when warm.

We'll have a look when this weather fucks off, as they're locking nuts rather than needing to buy a whole set of shims. Worst happens, it's not much additional work to getting all the gubbins off to remove the rubbers or get to/modify carbs.
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jaffa90
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PostPosted: 18:02 - 22 Feb 2020    Post subject: Reply with quote
"""Once it's warmed up, it runs as you would expect any IL4 600 to, and starts back up instantly if still warm/hot."""

What`s IL4??????????

If the valve clearances were too tight then higher revs would make it worse.
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ThatDippyTwat
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PostPosted: 20:07 - 22 Feb 2020    Post subject: Reply with quote
jaffa90 wrote:
"""Once it's warmed up, it runs as you would expect any IL4 600 to, and starts back up instantly if still warm/hot."""

What`s IL4??????????

If the valve clearances were too tight then higher revs would make it worse.

Inline 4.

It won't hurt to check them. It's not as if it's a huge hassle to take the cam cover and oil feeds off while tank etc are off anyway. If they're fine, I then know they're fine, and can move onto other things.
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Bhud
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PostPosted: 20:25 - 22 Feb 2020    Post subject: Reply with quote
If the revs aren't dropping quickly once the bike is warmed up, I'd suspect either a dirty throttle cable or return spring, or a vacuum leak (I know you checked this with the brake cleaner, but maybe check again). If it's not one of those things, then the carbs could be out of balance. I once wasted lots of time on out-of-balance carbs. The carbs were, in theory, clean and balanced, yet the bike would hang high when warm. I took the carbs off again and again, and set them all to open as equally as I could, on the bench. It made no difference. Then I discovered that a couple of the screws holding the bank of carbs together were loose. This was enough to produce a slight twisting motion so that one would move before the others, when they were put back on the bike and activated by the throttle cable.
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ThatDippyTwat
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PostPosted: 20:37 - 22 Feb 2020    Post subject: Reply with quote
Bhud wrote:
...or a vacuum leak (I know you checked this with the brake cleaner, but maybe check again). If it's not one of those things, then the carbs could be out of balance.

I've checked it a couple of times, it's the immediate thing that springs to mind, and it is over 20 years old. I'll lube and check the cable and springs, and make sure nothing it loose etc on the carbs.

It's annoying as other than the throttle dropping slowly, it was a hoot to ride when it was warm. I forgot how much the 600's, even the semi-skimmed ones like this, egg you on to give it more. The VFR has made me lazy indeed.
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mentalboy
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PostPosted: 01:06 - 23 Feb 2020    Post subject: Re: GSX600F - needs lots of choke until warm. Reply with quote
ThatDippyTwat wrote:
So, '98 GSX600F. Needs a fuckton of choke and held around 3-4K until properly warm - 5-10 mins.

I thought it was inlet rubbers leaking, but squirting brake cleaner around the rubbers while it was running didn't make it rev at all. Which is a pain as I have a set of inlet rubbers here.

So, I'm at a bit of a loss. Once it's warmed up, it runs as you would expect any IL4 600 to, and starts back up instantly if still warm/hot.
Ideas appreciated.


I had a '98 Teapot that was exactly the same, ugliest motherfucker bike I've had the mispleasure to own. I sold it as quick as I could...

Is yours red with a fuckton of previous owners? Laughing
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ThatDippyTwat
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PostPosted: 06:51 - 23 Feb 2020    Post subject: Re: GSX600F - needs lots of choke until warm. Reply with quote
mentalboy wrote:

I had a '98 Teapot that was exactly the same, ugliest motherfucker bike I've had the mispleasure to own. I sold it as quick as I could...

Is yours red with a fuckton of previous owners? Laughing


Red, but not that many owners.

They are ugly, almost 'Busa ugly. But it's a work hack, I'll be riding it, not looking at it.
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A100man
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PostPosted: 09:57 - 23 Feb 2020    Post subject: Reply with quote
ThatDippyTwat wrote:


However, a few people have suggested the valve clearances may be tight. Reason being she won't drop revs as quickly as she should, even when warm.



I agree with 'a few people' could also be a combination of things. inc a blockage in pilot circuit.
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MCN
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PostPosted: 10:32 - 23 Feb 2020    Post subject: Reply with quote
For the record.
Start using full choke. Don't phuque about with 1/2 3/4. It serves no purpose.
Just crack the throttle open and crank to start.
Gradually reduce choke setting as the engine warms up.
When engine can idle smoothly without cutting out then return choke to normal running position.

Cold weather will extend the time on choke.
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ThatDippyTwat
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PostPosted: 13:33 - 23 Feb 2020    Post subject: Reply with quote
MCN wrote:
...

No offence, but I'm well aware how to use a choke. You can't touch the throttle on startup, or it just wont start. When it does start, it will idle about 1500-2K for a few seconds. So far, that's what I expect, that or a minor variation of, is what I've experienced on any carb bike I've ever owned or ridden.

It then jumps to 4-5K without you doing anything whatsoever, not touching the choke or throttle, and wont let you back off the choke until its properly warm. 4-5K on choke is not normal for any bike I've ever ridden, irrespective of motor layout or number of cylinders. Warmup takes 10 mins or so. You can touch the throttle after 2 or 3, but it bogs like a demon even without load. If you try to ride it in any shape or form before you can drop the choke off altogether and idle at just over 1K, it'll bog and die. I'll get a vid later on if I get time.

Idea are gratefully recieved, but I'm not an idiot, despite what the forum name says. I'm trying not to be wordy and do a Teffers post, but I'm also trying not to miss out details that may or may not be important. If I'm cocking up, then tell me where, and why I can/can't/must do X, Y or Z.
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wr6133
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PostPosted: 14:59 - 23 Feb 2020    Post subject: Reply with quote
ThatDippyTwat wrote:

However, a few people have suggested the valve clearances may be tight.


I'm with a few people. It's the kind of bike that was bought and owned by the kind of people that don't actually like bikes and ignore jobs like that.
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sickpup
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PostPosted: 15:55 - 26 Feb 2020    Post subject: Reply with quote
What exhaust is on it? anything other than an original or a Motad would aslo cause these problems.
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MCN
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PostPosted: 16:17 - 26 Feb 2020    Post subject: Reply with quote
ThatDippyTwat wrote:
MCN wrote:
...

No offence, but I'm well aware how to use a choke. You can't touch the throttle on startup, or it just wont start. When it does start, it will idle about 1500-2K for a few seconds. So far, that's what I expect, that or a minor variation of, is what I've experienced on any carb bike I've ever owned or ridden.

It then jumps to 4-5K without you doing anything whatsoever, not touching the choke or throttle, and wont let you back off the choke until its properly warm. 4-5K on choke is not normal for any bike I've ever ridden, irrespective of motor layout or number of cylinders. Warmup takes 10 mins or so. You can touch the throttle after 2 or 3, but it bogs like a demon even without load. If you try to ride it in any shape or form before you can drop the choke off altogether and idle at just over 1K, it'll bog and die. I'll get a vid later on if I get time.

Idea are gratefully recieved, but I'm not an idiot, despite what the forum name says. I'm trying not to be wordy and do a Teffers post, but I'm also trying not to miss out details that may or may not be important. If I'm cocking up, then tell me where, and why I can/can't/must do X, Y or Z.


Have you checked the choke cable for damage/kinks/crimped?

The choke is probably easier to 'engage/apply as the cable pulls through the sheath. If the cable is broken inside or trapped then it won't be easy to fine control the choke towards off position.

The engine should increase RPM without touching anything.
That is why you need choke to make up fuel mixture lost to condensation on cold inlet passages.
As the engine warms then all of the choke enriched mixture reaches the combustion chamber.
So the more fuel more RPMs.
Then the choke lever can be moved to of gradually.

I thought you know how to work a choke? 🤔 Razz
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