M600 Finally sorted!!

tridentperu · 23-08-2021, 05:22 PM

Hi all,

Well it has taken me at least 6 months of fiddling about and frustration but I have finally, finally got my '99 M600 running as it should.

It was a non runner when I got it, so I sorted the wiring out and overhauled the fuel pump which wasn't pumping and got it going running. The carbs were clearly not right (I thought) as the bike ran fairly rich and one was overflowing all the time. So I took them off and gave them a refresh with new float and o ring kits from Allens - this stopped them flooding and the bike ran OK but was still rich. Float heights were spot on.

Various attempts and fiddling to no avail, it still ran rich and fouled plugs. Hotter plugs were better, but still not right.

Having got very good at taking the carbs on/off and not making much progress, I was beginning to think it might be electrical but went and sourced another set of carbs anyway, mainly for spares as they weren't in great shape - but they were cheap!

I knew my original carbs were ok but just couldn't quite figure out what was wrong - on the motorway, giving it plenty of throttle it was OK (just about) but it was low down/mid range that the farting and stuttering was at it's worst so I suspected worn needles/ jets. In the end I decided to swap out the needles and diaphrams from the 'new' carbs to see if there was any improvement.

When comparing parts the needles in the 'new' carbs were totally different! The old ones were pointed, the new ones almost parallel.

Swapped them over and set them in needle posn 3 - TRANSFORMED!!

Running just right, no plug fouling, no farting and missing. Still running the same set of plugs at the end of the week!

It turns out, after a lot of digging around, that the PO had fitted Dynojet needles with the std jets - no wonder it wouldn't run right!!

So - never underestimate what someone might have done previously, and what mismatched parts may be in there!

Hope this may help someone in the future. I am now running round on a bike that does what it should and is generally a pleasure to ride. I love it.

Jim

motomartin11 · 23-08-2021, 07:03 PM

Well done. Perserverance has paid off!
Having owned a succession of old bikes I totally understand.
My M750 has been one small problem after another-rear brake locking on ,neutral light switch wiring and other electrical issues ,fuel tank leaking to name but a few and yesterday I discovered a hole in one of the carbon end cans.

slob · 23-08-2021, 08:09 PM

great news, this thread deserves a picture

350TSS · 24-08-2021, 08:00 AM

Very satisfying when you overcome a problem with the bike, particularly if it is caused by interference by a previous owner. Well done

23-08-2021, 05:22 PM	#1
tridentperu Registered User Join Date: May 2019 Location: Gloucester Bike: M600 Posts: 32	M600 Finally sorted!! Hi all, Well it has taken me at least 6 months of fiddling about and frustration but I have finally, finally got my '99 M600 running as it should. It was a non runner when I got it, so I sorted the wiring out and overhauled the fuel pump which wasn't pumping and got it going running. The carbs were clearly not right (I thought) as the bike ran fairly rich and one was overflowing all the time. So I took them off and gave them a refresh with new float and o ring kits from Allens - this stopped them flooding and the bike ran OK but was still rich. Float heights were spot on. Various attempts and fiddling to no avail, it still ran rich and fouled plugs. Hotter plugs were better, but still not right. Having got very good at taking the carbs on/off and not making much progress, I was beginning to think it might be electrical but went and sourced another set of carbs anyway, mainly for spares as they weren't in great shape - but they were cheap! I knew my original carbs were ok but just couldn't quite figure out what was wrong - on the motorway, giving it plenty of throttle it was OK (just about) but it was low down/mid range that the farting and stuttering was at it's worst so I suspected worn needles/ jets. In the end I decided to swap out the needles and diaphrams from the 'new' carbs to see if there was any improvement. When comparing parts the needles in the 'new' carbs were totally different! The old ones were pointed, the new ones almost parallel. Swapped them over and set them in needle posn 3 - TRANSFORMED!! Running just right, no plug fouling, no farting and missing. Still running the same set of plugs at the end of the week! It turns out, after a lot of digging around, that the PO had fitted Dynojet needles with the std jets - no wonder it wouldn't run right!! So - never underestimate what someone might have done previously, and what mismatched parts may be in there! Hope this may help someone in the future. I am now running round on a bike that does what it should and is generally a pleasure to ride. I love it. Jim

23-08-2021, 07:03 PM	#2
motomartin11 Registered User Join Date: Sep 2010 Location: stourbridge Bike: M750 Posts: 352	Well done. Perserverance has paid off! Having owned a succession of old bikes I totally understand. My M750 has been one small problem after another-rear brake locking on ,neutral light switch wiring and other electrical issues ,fuel tank leaking to name but a few and yesterday I discovered a hole in one of the carbon end cans.

23-08-2021, 08:09 PM	#3
slob . Join Date: Jul 2003 Location: East London Bike: Multiple Monsters Posts: 9,714	great news, this thread deserves a picture

24-08-2021, 08:00 AM	#4
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,420	Very satisfying when you overcome a problem with the bike, particularly if it is caused by interference by a previous owner. Well done