M750 not running right. sort of????

[dunlop0_1]

M750 runs superb until in slow or stationary traffic and the bike gets hot then the revs rise quite a lot. Soon as the bike cools down the revs go back to normal. Any ideas or is this the norm for air cooled and carbs?
Thanks.
Neil.

[JamesM750]

This is not normal, my 750 (carb) does not do this even when hot. Does it only do this when idling, or does it also happen on acceleration?

You could try checking the easy stuff first such as the throttle linkage. If it only does it when hot then my guess is your idle speed is set OK, but may be worth a check.

If it is only at idle then erratic idling could be caused by incorrect amounts of air getting in, either by a knackered air filter or a leak at the carb.

[dunlop0_1]

Only does it at idle? Gonna check for leaks tomorrow......

[Chappers]

Rest assured my new toy, also a 750 was doing this yesterday when I picked it up...I was in town traffic for about half hour and the revs were flickering between 1-3k completely by itself and then when I got out of the traffic it was struggling to get power and was running lumpy as hell; thought she was gonna conk out at one point.

Pulled over, revved her to 6k then rode off and she was fine...until she started bleeding over 3hrs later in Cumbria :scratch:

[dunlop0_1]

Rest assured my new toy, also a 750 was doing this yesterday when I picked it up...I was in town traffic for about half hour and the revs were flickering between 1-3k completely by itself and then when I got out of the traffic it was struggling to get power and was running lumpy as hell; thought she was gonna conk out at one point.

Pulled over, revved her to 6k then rode off and she was fine...until she started bleeding over 3hrs later in Cumbria :scratch:

What do you mean by bleeding??????

[johnnystorm]

See Chappers' "thanks to gizmo" thread. The gearbox sprung a leak iirc. I'm no expert but I don't think the two incidents were related! ;)

[madhatter]

M750 runs superb until in slow or stationary traffic and the bike gets hot then the revs rise quite a lot. Soon as the bike cools down the revs go back to normal. Any ideas or is this the norm for air cooled and carbs?
Thanks.
Neil.

Try turning the handlebars from full lock left to full lock right, it could be that the throttle cable is snagged somewhere. If not, what revs are you running when ticking over from "cold", when you release the choke? It may just be a balance between when running cold and hot.

[rebel]

Mine is running rough when cold and keeps stalling, but it is ok once it has got hot. I think I just need to adjust my tickover up a touch!

[Chappers]

It ran really rough from the moment I left Nialls for about half hour in traffic but was fine when I was on the motorway and was running lovely til I got to about an hour away from home...that's when the weird noise appeared and the oil started leaking out :(

I don't have the bike in my possession at the min so can't check or do anything that anyone may advise but Niall has been ace and kept in constant contact with me and is sorting.

I'm praying that it's something as simple as a gasket but it didn't feel good when trying to get out of 2nd gear.

[dunlop0_1]

Checked the bike over yesterday, could not find anything wrong at all. I thing its just a Ducati thing. Will post if it develops.....

[Spike]

Had this problem with my 900 this stopped when the bike was stage 2 jetted so I would suspect the jetting

[eonan]

Checked the bike over yesterday, could not find anything wrong at all. I thing its just a Ducati thing. Will post if it develops.....

Bottom line is no, its not 'a Ducati thing'. No bike should run like this...period!

There could be a number of reasons, jetting is the obvious one...was this always happening with your bike though? If not, it might not be anything to do with jetting. I'm wondering if both cylinders are firing properly? Switching between one and two would probably give this effect.

Hayley, when you say lumpy, just how lumpy was it? You describe 'loosing power'...did it feel as if could have been switching to one cylinder? When you say you stopped to rev it, how hard did you rev it? If it was only running on one cylinder that might not have such a good thing :worried: Of course I could be talking complete bollocks :o

dunlop0_1 most of the people who will be able to help you are away at the weekender. They should be back sometime today though, so hopefully they'll be along later to shed some more light on things :thumbsup:

[Chappers]

Hayley, when you say lumpy, just how lumpy was it? You describe 'loosing power'...did it feel as if could have been switching to one cylinder? When you say you stopped to rev it, how hard did you rev it? If it was only running on one cylinder that might not have such a good thing :worried: Of course I could be talking complete bollocks :o


That sounds exactly what it could of been, it was live driving a car with a turbo but the turbo not working at stages if you get my meaning but then it would jerk all over the place hence the lumpy description.

Only revved to 6k, in fact never rode the bike over 6k although the rev counter was flickering all over the place when riding - really lose looking needle, but the needle was defo telling the truth when stationery or slow manouvering coz you could feel and hear the difference from 1-3k...that was no flicker.

[eonan]

That sounds exactly what it could of been, it was live driving a car with a turbo but the turbo not working at stages if you get my meaning but then it would jerk all over the place hence the lumpy description.

Only revved to 6k, in fact never rode the bike over 6k although the rev counter was flickering all over the place when riding - really lose looking needle, but the needle was defo telling the truth when stationery or slow manouvering coz you could feel and hear the difference from 1-3k...that was no flicker.

I'm having sleepness nights trying to think what might have happened :( I feel pretty useless just sitting here not being able to do anything until we can get the bike into Ducati :banghead:

[Chappers]

It's giving me brain ache so I'm just waiting to see what Ducati say once it goes in :scratch:

[JamesM750]

Checked the bike over yesterday, could not find anything wrong at all. I thing its just a Ducati thing. Will post if it develops.....

You could also have a quick look over the fast idle lever/linkage. How about whipping off the air filter, letting it get hot and seeing if either the throttle or fast idle is operating the butterfly valve?

[Shandy]

M750 runs superb until in slow or stationary traffic and the bike gets hot then the revs rise quite a lot. Soon as the bike cools down the revs go back to normal. Any ideas or is this the norm for air cooled and carbs?
Thanks.
Neil.

No it's not right, Stef posted this link up on a thread for me a while ago and it worked a treat for mine.

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html

If you have a read there are several things that affect the revs at stationary, i think you're maybe running a bit lean from reading 'part 4 idle and low rpm cruise'

Good luck with it, a bit of perserverance it gets there in the end!!!

Cheers,

Shandy

[barbican]

Checked the bike over yesterday, could not find anything wrong at all. I thing its just a Ducati thing. Will post if it develops.....

Sounds like an air leak in the carb/manifold area, possibly worn throttle slides (if these carbs have them). Only know old british stuff used to do this when the Amal carbs got a little worn, or inlet gasket sh*gged, and too much air gets in, only noticible from fast idle since at higher throttle the difference in air flow is minimal.

To check gaskets/manifold leaks spray a little wd/carb cleaner on joints and see if engine note changes, to check slides strip the carbs