M750 carb balancing help please.

Brian. · 13-02-2023, 10:13 AM

Good morning all,

I've done most of the work needed to recommission my 1998 M750, and as part of this work I'd like to balance my carbs. They are not far out, but out they definitely are, as checked on my Carbtune.

The problem I'm having is accessing the balancing screw. It can just about see it, using a long LED light and a mirror. Is that how it's done? I can just about get a long thin screwdriver to it, but it's so difficult because using the mirror it's all back to front, ie I have to move the screwdriver the opposite way than it would appear. And that's just practicing, without the engine running.

It would be easier if I could drop the oil cooler down out of the way. I've removed the fixing screws, but the cooler will hardly move down at all; my bike is the later engine M750, and it has the carb heater system ie oil pipes to the float bowls etc., and there is virtually no "give" in the pipework.

Am I missing something here? Have I got the wrong idea here? Is there an easier way? Or is this just how it's done?

Any advice will be very gratefully received as ever.

Thank you! Brian.

jerry · 13-02-2023, 10:56 AM

It is very fiddly I have 3 carbed 750s all with oil cooler so plenty of practice ,, you need a long philips screwdriver , and torch . lie on you back on ground is best remove oil cooler for better access is a good idea it should pivot down under front head the hoses do flex enough but dont scratch mudguard , dont bother with mirror

Brian. · 13-02-2023, 02:01 PM

Hi Jerry,

Thank you for replying.

Do any of your bikes have the pipework to divert some of the engine oil through some pipework to the carb float chambers? Presumably, to do something about carb icing?

On the RHS (sitting on the bike) oil cooler has a T-piece in it, with a tap which is presumably to turn this system off in warmer weather? Because of this, and the braided hose that goes from this tap to the float bowls, even if I unbolt the oil cooler this pipework prevents me moving the oil cooler down out of the way.

The pipework from this tap goes from the RH oil cooler feed pipe to the RH float bowl, then to the LH float bowl, and from there another pipe returns back to the side of the RH oil cooler connection.

I have (I think!) attached three photos of this tap & pipework. Do any of yours have this system?

Thank you, Brian.

Edit - uploading the photos failed, I'll try again on a separate posting.

Brian. · 13-02-2023, 02:18 PM

Hi again!

Try again with the oil tap & pipe photos.....

https://www.dropbox.com/s/dez1j9gc1s...20tap.JPG?dl=0
https://www.dropbox.com/s/skajbofv44...pipes.JPG?dl=0
https://www.dropbox.com/s/8kqp3nuubt...union.JPG?dl=0

Hopefully those links will work.

Thank you again, Brian

jerry · 13-02-2023, 06:11 PM

my 2000 monster has electric carb heaters the 1997 monster and 750ss dont have any carb heaters at all and never had any real problems even in cold weather,,

Brian. · 13-02-2023, 06:20 PM

Thank you; for me right now the damn things are jut in the way!

I'l just have to see how I get on, I want it all done for 1st March, I'm planning to re-tax it then.

Regards, Brian.

Mr Gazza · 13-02-2023, 06:56 PM

My first M900 had the oil carb warmers and I found that they worked well against icing.
I got tuned into the conditions that caused the icing and learned to turn the warmers on before it happened.

I'm not sure how they attach to the carbs, but I would imagine they are banjos?
I think you should be able to run the bike with the banjos disconnected, provided you turn the warmers off at the diverter tap. The lever points down the pipe that flows, so you point the lever up the warmers towards the carbs to divert oil that way and down the line directly to cooler to send it that way.
The lines do tee together at the cooler, so you might get a bit of back flow from that direction if you run it with the connections off. Chances are it's going to be messy just taking them off so I guess you have to allow for that!!

Brian. · 13-02-2023, 07:05 PM

Thanks Mr Gazza, I was thinking about having to do that.

What a bloody faff just to turn a screw for what will in reality be just a fraction of a turn.

Oh well, the pleasures & joys of motorcycle maintenance eh!

Thank you.

Darren69 · 13-02-2023, 08:01 PM

What he said. Maybe one of those boroscope thingies that plug into s smart phone would help too?

https://www.ebay.co.uk/itm/403719103...mis&media=COPY

Brian. · 13-02-2023, 09:04 PM

Quote:

Originally Posted by Darren69

What he said. Maybe one of those boroscope thingies that plug into s smart phone would help too?

https://www.ebay.co.uk/itm/403719103...mis&media=COPY

Now that's a thought, if all else fails that's something to fall back on.

Thank you.

Sirc · 14-02-2023, 01:45 AM

As Jerry says, dropping the whole oil cooler down with hoses still attached definitely helps but (only my opinion) think twice about removing hose connections on carb bowls as it's really difficult to re-attach banjos because the hoses are rarely "in repose" so lots of struggling to get fixing perpendicular to tapping (x 4) not to mention juggling with copper/fibre washers (x 8) on re-attaching. I always used to paint head of balancing screw with a dab of white paint to help locate and also so as not to confuse with slow-running screw in similar location as I got older and more forgetful. If it's a keeper, you might consider obtaining and replacing slow-running screw with a remote (cable operated) equivalent* which makes that part of the job luxury ever after. Although sometimes trickier, I never found oil cooler hoses stopped me getting at balance screw or slow-running screw on several vehicles.

* as fitted to Yamaha FZR etc.

Darren69 · 14-02-2023, 11:36 AM

It looks as though you might be able to split the hose apart near the tap, but as mentioned in the previous post the carb float bowl banjos are probably best left alone, they are a swine to get back.

Brian. · 14-02-2023, 12:57 PM

Thank you Sirc and Darren for the last two postings. I'm otherwise occupied now until Sunday; unless I can find a spare hour in the meantime I won't be able to have another go at it until then.

I'll post on here whatever I end up doing.

Thank you, Brian.

Mr Gazza · 14-02-2023, 01:43 PM

By the sound of it you're going to be better off leaving the oil lines alone. It looks like more trouble than finding the screw head.
I wonder if it's possible to push a tube of some sort into place that would guide the screwdriver into place within a bit?
I'm thinking along the lines of passing a bit of tube over the screwdriver and then guiding it carefully onto the screw, with assistance. Next, lodge the tube in place with whatever it takes, maybe cardboard and hot glue? Obviously a two handed job to hold the screwdriver whilst a n other is trying to fix the tube in place. Hot glue picks off most things with no damage, so you could go mad with it.
If it worked you could then probably find the screw head blind. Y' never know it might just work? Glad my bikes don't have carbs..

Brian. · 14-02-2023, 03:28 PM

I think that's a good idea Gazza. I might do that when I can get back to it.

I was going to whip the airbox off & have a look at the carbs the other day, but when I had a look I realised that the airbox doesn't just "whip off". It's battery & electrics off too by the looks of things, and I decided to leave it until I had time to do that in one go.

I think I'm going to do that.

My only concern in putting a bit of tube on the balancing tube is that it might in some way hamper the operation of them, by making them not shut down at some point.

Yup, I'll do that either Sunday or more likely Monday

Thank you.

13-02-2023, 10:13 AM	#1
Brian. Registered User Join Date: Sep 2022 Location: Little Haywood Bike: M750 Posts: 68	M750 carb balancing help please. Good morning all, I've done most of the work needed to recommission my 1998 M750, and as part of this work I'd like to balance my carbs. They are not far out, but out they definitely are, as checked on my Carbtune. The problem I'm having is accessing the balancing screw. It can just about see it, using a long LED light and a mirror. Is that how it's done? I can just about get a long thin screwdriver to it, but it's so difficult because using the mirror it's all back to front, ie I have to move the screwdriver the opposite way than it would appear. And that's just practicing, without the engine running. It would be easier if I could drop the oil cooler down out of the way. I've removed the fixing screws, but the cooler will hardly move down at all; my bike is the later engine M750, and it has the carb heater system ie oil pipes to the float bowls etc., and there is virtually no "give" in the pipework. Am I missing something here? Have I got the wrong idea here? Is there an easier way? Or is this just how it's done? Any advice will be very gratefully received as ever. Thank you! Brian. Last edited by Brian.; 13-02-2023 at 10:16 AM..

13-02-2023, 10:56 AM	#2
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,816	It is very fiddly I have 3 carbed 750s all with oil cooler so plenty of practice ,, you need a long philips screwdriver , and torch . lie on you back on ground is best remove oil cooler for better access is a good idea it should pivot down under front head the hoses do flex enough but dont scratch mudguard , dont bother with mirror __________________ MONSTERMAN

13-02-2023, 02:01 PM	#3
Brian. Registered User Join Date: Sep 2022 Location: Little Haywood Bike: M750 Posts: 68	Hi Jerry, Thank you for replying. Do any of your bikes have the pipework to divert some of the engine oil through some pipework to the carb float chambers? Presumably, to do something about carb icing? On the RHS (sitting on the bike) oil cooler has a T-piece in it, with a tap which is presumably to turn this system off in warmer weather? Because of this, and the braided hose that goes from this tap to the float bowls, even if I unbolt the oil cooler this pipework prevents me moving the oil cooler down out of the way. The pipework from this tap goes from the RH oil cooler feed pipe to the RH float bowl, then to the LH float bowl, and from there another pipe returns back to the side of the RH oil cooler connection. I have (I think!) attached three photos of this tap & pipework. Do any of yours have this system? Thank you, Brian. Edit - uploading the photos failed, I'll try again on a separate posting. Last edited by Brian.; 13-02-2023 at 02:04 PM..

13-02-2023, 06:11 PM	#5
jerry Old Git Join Date: May 2006 Location: Cricklade Bike: Multiple Monsters Posts: 2,816	my 2000 monster has electric carb heaters the 1997 monster and 750ss dont have any carb heaters at all and never had any real problems even in cold weather,, __________________ MONSTERMAN

13-02-2023, 06:56 PM	#7
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,805	My first M900 had the oil carb warmers and I found that they worked well against icing. I got tuned into the conditions that caused the icing and learned to turn the warmers on before it happened. I'm not sure how they attach to the carbs, but I would imagine they are banjos? I think you should be able to run the bike with the banjos disconnected, provided you turn the warmers off at the diverter tap. The lever points down the pipe that flows, so you point the lever up the warmers towards the carbs to divert oil that way and down the line directly to cooler to send it that way. The lines do tee together at the cooler, so you might get a bit of back flow from that direction if you run it with the connections off. Chances are it's going to be messy just taking them off so I guess you have to allow for that!! __________________

13-02-2023, 02:18 PM	#4
Brian. Registered User Join Date: Sep 2022 Location: Little Haywood Bike: M750 Posts: 68	Hi again! Try again with the oil tap & pipe photos..... https://www.dropbox.com/s/dez1j9gc1s...20tap.JPG?dl=0 https://www.dropbox.com/s/skajbofv44...pipes.JPG?dl=0 https://www.dropbox.com/s/8kqp3nuubt...union.JPG?dl=0 Hopefully those links will work. Thank you again, Brian

13-02-2023, 06:20 PM	#6
Brian. Registered User Join Date: Sep 2022 Location: Little Haywood Bike: M750 Posts: 68	Thank you; for me right now the damn things are jut in the way! I'l just have to see how I get on, I want it all done for 1st March, I'm planning to re-tax it then. Regards, Brian.

13-02-2023, 07:05 PM	#8
Brian. Registered User Join Date: Sep 2022 Location: Little Haywood Bike: M750 Posts: 68	Thanks Mr Gazza, I was thinking about having to do that. What a bloody faff just to turn a screw for what will in reality be just a fraction of a turn. Oh well, the pleasures & joys of motorcycle maintenance eh! Thank you.

13-02-2023, 08:01 PM	#9
Darren69 Transmaniacon MOC Join Date: Sep 2013 Location: Sutton In Ashfield Bike: Multiple Monsters Posts: 6,022	What he said. Maybe one of those boroscope thingies that plug into s smart phone would help too? https://www.ebay.co.uk/itm/403719103...mis&media=COPY __________________ Roast Beef Monster! Termignoni and Bucci - Italian for pipe and slippers! S4 Fogarty, S4R 07T, 748, Series 1 Mirage

14-02-2023, 01:45 AM	#11
Sirc Registered User Join Date: Jul 2008 Location: guildford Bike: M1200R Posts: 369	As Jerry says, dropping the whole oil cooler down with hoses still attached definitely helps but (only my opinion) think twice about removing hose connections on carb bowls as it's really difficult to re-attach banjos because the hoses are rarely "in repose" so lots of struggling to get fixing perpendicular to tapping (x 4) not to mention juggling with copper/fibre washers (x 8) on re-attaching. I always used to paint head of balancing screw with a dab of white paint to help locate and also so as not to confuse with slow-running screw in similar location as I got older and more forgetful. If it's a keeper, you might consider obtaining and replacing slow-running screw with a remote (cable operated) equivalent* which makes that part of the job luxury ever after. Although sometimes trickier, I never found oil cooler hoses stopped me getting at balance screw or slow-running screw on several vehicles. * as fitted to Yamaha FZR etc. __________________ giacca a vento massima

14-02-2023, 11:36 AM	#12
Darren69 Transmaniacon MOC Join Date: Sep 2013 Location: Sutton In Ashfield Bike: Multiple Monsters Posts: 6,022	It looks as though you might be able to split the hose apart near the tap, but as mentioned in the previous post the carb float bowl banjos are probably best left alone, they are a swine to get back. __________________ Roast Beef Monster! Termignoni and Bucci - Italian for pipe and slippers! S4 Fogarty, S4R 07T, 748, Series 1 Mirage

14-02-2023, 12:57 PM	#13
Brian. Registered User Join Date: Sep 2022 Location: Little Haywood Bike: M750 Posts: 68	Thank you Sirc and Darren for the last two postings. I'm otherwise occupied now until Sunday; unless I can find a spare hour in the meantime I won't be able to have another go at it until then. I'll post on here whatever I end up doing. Thank you, Brian.

14-02-2023, 01:43 PM	#14
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,805	By the sound of it you're going to be better off leaving the oil lines alone. It looks like more trouble than finding the screw head. I wonder if it's possible to push a tube of some sort into place that would guide the screwdriver into place within a bit? I'm thinking along the lines of passing a bit of tube over the screwdriver and then guiding it carefully onto the screw, with assistance. Next, lodge the tube in place with whatever it takes, maybe cardboard and hot glue? Obviously a two handed job to hold the screwdriver whilst a n other is trying to fix the tube in place. Hot glue picks off most things with no damage, so you could go mad with it. If it worked you could then probably find the screw head blind. Y' never know it might just work? Glad my bikes don't have carbs.. __________________

14-02-2023, 03:28 PM	#15
Brian. Registered User Join Date: Sep 2022 Location: Little Haywood Bike: M750 Posts: 68	I think that's a good idea Gazza. I might do that when I can get back to it. I was going to whip the airbox off & have a look at the carbs the other day, but when I had a look I realised that the airbox doesn't just "whip off". It's battery & electrics off too by the looks of things, and I decided to leave it until I had time to do that in one go. I think I'm going to do that. My only concern in putting a bit of tube on the balancing tube is that it might in some way hamper the operation of them, by making them not shut down at some point. Yup, I'll do that either Sunday or more likely Monday Thank you.