Balancing carbs and adjusting idle

[Devilman]

Forgive me if this has already been suggested, I've not had the chance to read all the recommendations made by others....

I had a similar issue with a 750J a while back, no matter how hard I tried to get the carbs balanced, I would end up with the idle "hanging up" like you describe. 

Turns out it was vacuum leaks due to cracked / perished carb rubbers (and the O-Rings behind them). 

Could be worth a try?

[Omegasteve]

7 hours ago, coombehouse said:

I can't see valve clearance causing that though I could be wrong. It certainly wouldn't make it idle high. The most likely is still an airleak at the carb rubbers or a blockage internally in the carbs  

If there is a blockage then at this point I have no idea where it will be. Everything blows through clear and I've also gently run wire through almost all of the passageways too. Granted I may need to go that extra step and sonic clean them. I just can't believe there's anything left to come out of them. Rubbers all seem in good condition and I can't see any splits or tears either. 

[Lachie04]

Just to throw it out there I had trouble with my 750 F carbs and was convinced it was the choke. I found one of the boot rubbers into the airbox loose reglued it like the others with contact adhesive and sorted my running issues so when you check rubbers for leaks also check fitting into the airbox (not saying its the not running thing though)

[Omegasteve]

8 hours ago, Devilman said:

Forgive me if this has already been suggested, I've not had the chance to read all the recommendations made by others....

I had a similar issue with a 750J a while back, no matter how hard I tried to get the carbs balanced, I would end up with the idle "hanging up" like you describe. 

Turns out it was vacuum leaks due to cracked / perished carb rubbers (and the O-Rings behind them). 

Could be worth a try?

Definitely worth a try! Any ideas where to get them? 

[Omegasteve]

8 hours ago, coombehouse said:

I can't see valve clearance causing that though I could be wrong. It certainly wouldn't make it idle high. The most likely is still an airleak at the carb rubbers or a blockage internally in the carbs  

Although I won't dismiss the possibility of a blockage of course 

[davecara]

16 minutes ago, Omegasteve said:

Definitely worth a try! Any ideas where to get them? 

*if* theyve still got them, Lidl had a selection box of O rings and there was half a dozen in there the right size for the inlet rubbers. I reckon your pilot circuits are blocked though

[Omegasteve]

8 minutes ago, davecara said:

*if* theyve still got them, Lidl had a selection box of O rings and there was half a dozen in there the right size for the inlet rubbers. I reckon your pilot circuits are blocked though

I'll strip the carbs down again and bring them over to you if the offer is still open?

[davecara]

Yeah of course mate, give me some notice to buy some cleaning solution!

[Omegasteve]

Just now, davecara said:

Yeah of course mate, give me some notice to buy some cleaning solution!

Thanks so much bud, I'll get them stripped down this weekend but I won't bother you over the festive period. Let me know how much you want to cover it and I'll make sure to square you up. 

[davecara]

6 minutes ago, Omegasteve said:

Thanks so much bud, I'll get them stripped down this weekend but I won't bother you over the festive period. Let me know how much you want to cover it and I'll make sure to square you up. 

Its all good dont worry, just bring cake 

[Omegasteve]

7 minutes ago, davecara said:

Its all good dont worry, just bring cake 

Sounds good to me. You tell me what weekend is best and I'll be there 

[Omegasteve]

Also, im guessing its mk1 bandit carb rubbers that will be the replacement ones? 

[Devilman]

1 hour ago, Omegasteve said:

Also, im guessing its mk1 bandit carb rubbers that will be the replacement ones? 

Not certain on that one, but you could try using one of the online parts catalogues (such as cmsnl or fowlers) to cross-check the part rubber numbers to see if they're the same

[davecara]

Unless theyre damaged, you wont need to replace the carb rubbers themselves, just the O rings. Just be dead careful taking the JIS screws out that hold them on. Dont try and do it with a Phillips screwdriver as it'll cam out and damage the head of the screw

If you cant find the Lidl ones, you'll want 4 of 0928040020 from Suzuki. Theyre only about £4 a throw. might be a quid cheaper off Grumpys

 

 

O Ring(d:2.4,id:43.2)  is the size btw

 

Edited December 14, 2022 by davecara

[Omegasteve]

4 minutes ago, davecara said:

Unless theyre damaged, you wont need to replace the carb rubbers themselves, just the O rings. Just be dead careful taking the JIS screws out that hold them on. Dont try and do it with a Phillips screwdriver as it'll cam out and damage the head of the screw

If you cant find the Lidl ones, you'll want 4 of 0928040020 from Suzuki. Theyre only about £4 a throw. might be a quid cheaper off Grumpys

 

Fantastic,  what's grumpys? 

[davecara]

8 minutes ago, Omegasteve said:

Fantastic,  what's grumpys? 

http://grumpy1260suzukispares.co.uk/index.php/contact/

 

Or the Grumpy1260 page on faceache 

[Omegasteve]

Sweet, just messaged them

[Omegasteve]

19 minutes ago, davecara said:

http://grumpy1260suzukispares.co.uk/index.php/contact/

 

Or the Grumpy1260 page on faceache 

Just to double check, csmnl list the size as 2.4x39.7mm. Which is correct? If not sure I'll just measure mine of course. 

[davecara]

6 minutes ago, Omegasteve said:

Just to double check, csmnl list the size as 2.4x39.7mm. Which is correct? If not sure I'll just measure mine of course. 

I think they'll all interchange to be honest, if you follow all the part number supercessions on cmsnl theres a dozen or more sizes all listed as being compatible with each other

[Omegasteve]

1 hour ago, davecara said:

I think they'll all interchange to be honest, if you follow all the part number supercessions on cmsnl theres a dozen or more sizes all listed as being compatible with each other

Nice, I'll have a hunt whilst I wait for grumpys to reply. Bearingshopuk list the size in a nitrile oring x5 for £1.51. 

Edited December 14, 2022 by Omegasteve

[davecara]

8 minutes ago, Omegasteve said:

Nice, I'll have a hunt whilst I wait for grumpys to reply. Bearingshopuk list the size for £1.51 in a nitrile oring x5 for £1.51. 

Be worth buying a dozen at that price!

[Omegasteve]

1 hour ago, davecara said:

Be worth buying a dozen at that price!

Haha bought some to check the fit. Got to be worth a look in my eyes. 

[bluedog59]

Just a random thought but how about that the carbs are so far out of balance that 1 or more of the butterflies are actually totally shut ? This may result in no air flow for the pilot jets to work with on the carb(s) affected. Raising the tickover would bring them into play for it to run on all 4. Maybe balancing the carbs by eye to start with or balancing with the gauges on a high tickover may help.

[Omegasteve]

9 minutes ago, bluedog59 said:

Just a random thought but how about that the carbs are so far out of balance that 1 or more of the butterflies are actually totally shut ? This may result in no air flow for the pilot jets to work with on the carb(s) affected. Raising the tickover would bring them into play for it to run on all 4. Maybe balancing the carbs by eye to start with or balancing with the gauges on a high tickover may help.

Hi bud thank you for your reply, I've set them up by eye first of all with thr butterfly sitting slightly behind the third of the three small holes. I've also did my best to balance them at a 2k idle and managed to get them all into 1cm/hg or whatever it is of each other. 

[TonyGee]

I set the butterflies up on the bench first, open the idle screw a fare bit so you can get a thin drill bit under one, then set the rest the same.  then you can do them on the bike with the gauges.  (dont forget to adjust the idle screw before starting)