PDA

View Full Version : Carbs again


Stued
29-05-2013, 08:00 PM
Monster M600 1996 on a Q Plate (brought out the shed after a 5 year sabbatical)

Problem is I can't get it to idle at below what seems to be 2K revs or more, and when revved, revs rise and then return to an idle higher than it was for a time before dropping to original revs.

Stripped and cleaned the carbs, set the float heights to 14mm (were 9mm) ultrasonically cleaned and blew through all the drillings, rebuilt them and have to say it seems better, but cannot get the idle below 2K without it dying.

Done static timing and changed the belts, new plugs, took both HT leads off and cut 1'' off each end and reassembled them

Found that the return throttle cable to be a bit s**t so for the moment that's off, and the remaining throttle cable has been lube'd and moves freely, throttle quadrant has been cleaned up and moves freely and snaps back when released.

Fuel pump (vacuum) stripped and cleaned and reassembled, new vacuum lines to both pump and tap replaced with new.

will get a Colour Tune tomorrow to check the mixture

Right I know I'm going to be told to use the search function, but you see the thing is I have, and found contradictory results. everyone seems to agree that the float height is 14mm, but there is some confusion (maybe its me) as to the pilot screws and whether in is lean out is rich or vise versa and a standard setting (come on its a Monster, NOTHING is standard!)

Thing is its really peeing me off, its not like I don't know what I'm doing, built a ZXR750 Kawasaki France Endurance Racer clone from a box of bits, a ZXR / T595 / GSXR hybrid that started off as someone else's streetfighter. used to live in the middle of nowhere near Aberdeen but now live in a rural village near Great Yarmouth with a Monster with Yoshi straight through silencers (s******). I think I may have upset the neighbours. Eva is now boarding up the doors and the windows

JuZ
29-05-2013, 08:23 PM
Out to richen.

Dookbob
30-05-2013, 06:34 PM
Juz has it right, in is lean, out is rich. You seem to have done everything in the way of cleaning the carbs, but it does sound like the slow running and progression holes could still be blocked. I would be inclined to source a second hand pair of carbs off a bike that was running not long ago. Five years is a long time for carbs to be lying around, those tiny holes in the slow running and progression drillings could be oxidised solid by now, and if thats the case, ultrasonics probably wouldn't clear them.

Stued
04-06-2013, 07:43 AM
thanks for the replies, cabs stripped again and probes in use.....

gary tompkins
04-06-2013, 10:49 PM
M750 and M900 carbs will work as well with the right jets installed, and Yamaha's TDM850 uses the same carb as well

May give you a few options if sourcing replacements

http://www.ebay.co.uk/itm/DUCATI-750SS-900-750-600-SS-MIKUNI-CARBS-/181142884051?pt=UK_Motorcycle_Parts_13&hash=item2a2cf50ed3

http://www.ebay.co.uk/itm/DUCATI-750-SS-750SS-MIKUNI-CARBS-/171048491790?pt=UK_Motorcycle_Parts_13&hash=item27d348db0e

gary tompkins
04-06-2013, 10:59 PM
Assuming your pilot screws are not seized in it may be worth considering swapping to these?

http://www.ebay.co.uk/itm/Fuel-Screw-extended-Ducati-400-600-750-900-w-38mm-Mikuni-carbs-3020m1x-xxx-/290872532270?pt=Motorcycles_Parts_Accessories&hash=item43b95a9d2e

Stued
05-06-2013, 06:59 AM
Now then lots to think about

Will look into it thanks Gary

Dookbob
05-06-2013, 09:21 AM
I really , really like those extended idle screws, trust the Yanks to come up with EXACTLY what was required.

mholc123
07-06-2013, 06:35 AM
What about the rubber diaphram in the top of the carbs, is this OK, I believe if you have an split in one of those it will give you the systems that you explained.

Sirc
07-06-2013, 03:29 PM
true ^ or an air leak at manifold rubbers or a maladjusted balance screw where the slave carb butterfly is opened a lot more than the 'master' (i.e. even if slow running screw wound completely out, engine revs could still be high)

urbanfireblade
09-06-2013, 06:36 PM
Cheapest option looking back when i had carb trouble was to just bolt on another pair of carbs. I spent a fortune on needles, jets, springs etc etc when a £60 set of m900 carbs onto my m600 solved the problem. Wish i'd done that in the first place.

Stued
09-06-2013, 07:14 PM
Am looking, but whats out there is bigger than my budget!!

urbanfireblade
12-06-2013, 05:01 PM
Maybe post a wanted on here, thats how i got mine, 60quid posted, from a monster 900 that had done just 8k. eBay is a bit of a lottery tbh, just have to suss out the genuine sellers from the dealers/breakers.

Gilps
12-06-2013, 05:37 PM
I've got a set from a 600, fitted with dynojet stage 2 kit, and oil cooler bowl lids, and oil lines too, going spare. Long story cut short, they may be ok but there was a possible problem with them.

Any good to you? Let me know and ill go into details if you are interested.