Problems running my Domi.

[Robroy]

Hi.

I have a Domi 650 89 mod. that i have built to a motard.
I have a problem with my bike.
What i did:
I changed the carburettor to a XR600R carb. to see if the problem went away. The bike started fine and run nice for 5 min then it died out and would not start, it backfires into the carburettor.
So i took it off again and took the original carburettor on again to see if it would run, since i had a problem with this also before i changed tto the XR600R carb. My problem with this carb is that the bike starts very easy and runs beatiful without any throttle. I can take just barely on the throttle so that the bike will go up to about 2000 rpm and thats all. If i try with more throttle hard or small is just the same, It backfires into the carb and will stall at once. The bike will start at once again without any throttle and runs nice again, but if i give throttle then it does the same again backfires hard and dies.

Maby someone can help me out??

[joch]

sounds like you're running too lean. if you haven't changed anything (air-filter or pulled snorkel from the airbox) i would clean the carb. i once pulled the snorkel from the airbox in combination with a k&n filter and the same happened.
hope that helps

[Robroy]

Sorry since i did not mention this before. I haven't connected mit carburettor to the filterbox/hose since my filterbox is cracked and therefore broken. It's without any filter for now so the carb is directly into the free air. This will cause a big problem then?

[joch]

yes, also bear in mind that a little dirt can ruin your engine!

[Simon WS]

Yes - get an airfilter of some sort on there quick to avoid sucking lumps of debris into your engine! I scrapped the airbox on mine and use a nice K&N pod style filter (K&N number SN -2570). Works great, but a lot more noisy.
I had exactly the symptoms you had with another of my bikes that uses the same Honda CV carb - BUT that doesn't mean your solution will be the same!
Basically, the problem I discovered was that the CV diaphragm was not sealing (or could be split) and so the slide does not lift properly causing huge richness at anything off idle (and black smoke and backfiring). BTW try to cure the problem immediately because a backfire can easily destroy your one way starter clutch which is quite expensive and a real pain to change!

My only concern with the above diagnosis is that you say the behaviour is the same with both the carbs - I guess it is possible they both have the same fault, but??...

If you have a mate with a working bike the easiest way of confirming it is to swap the carb over which is relatively easy.

Good luck,
Simon

[Rubberchicken]

If you don't have an airbox on then both carbs will have the same problem ofcourse.

Something very simple to try: Put your hand over the air intake so that you leave a smaller hole, and see if it'll rev like that.

Basically 2 solutions:
1. Get an airbox. Easy fix.
2. Alter the jetting for running without the airbox. This will mean a (much) bigger main jet, and then work down from there. (Meaning first the main jet, then the needle, then the idle mixture. This is an arse of a job on the dommie, but it needs to be done. Just tweaking the idle mixture won't do squat to fix this, don't let anyone tell you otherwise. )

Though you'd best put some kind of filter on to avoid sucking in grit, birds, stray sheep, and small children. And possibly your pant leg.

[Simon WS]

Whilst running without the airbox will obviously change the air/fuel ratio and will need correcting by re-jetting, it won't cause the depth of problems the Poster has. I'm sure about this because I have tried it!
The symptoms point to either the slide not moving correctly or the choke stuck IMHO.
I'd definitely check out the diaphragm if I were you.

Simon

[Robroy]

Finally i got the filterbox and fitted everything together.
Started the bike but its just the same.
It starts very easy, i use the kicker to start it. starts on first punch.
Its a little bettert though, now i can have the bike at full throttle only if i have the choke fully on and jank the throttle some time to get the rpm over 5000 or so then the throttle goes to max without a problem. But if i let the bike go down to slow and then try to increase the throttle just slowly it dies, it backfires. If i take off the choke it starts with no problem with no throttle and has no problem up to 2000 rpm, over this it just gives me a puff and dies.
I hav another CDI new one but just the same ther also.

[AJsgp]

may i know what are the sizes of your jettings?i mite continue the saga with my XR600R carb..