Where to buy Mikuni jets?

[JimF]

I may be premature with this post - but I tend to be over-cautious where my Ducatis are concerned.

I had a 190 main jet, the plug was getting sooted up and the engine would cut out at 6000 rpm. The previous owner admitted that the bike would do exactly the same for him (and this I did not know before today), so my changing to a baffled megaphone and replacing the air filter element was probably not the tipping point when it comes to this rev limit problem.

I got two new jets in the mail today. A 185 and a 180.

I am currently waiting on new plugs to be delivered; BR9HIX Iridium plugs. I am currently using the non-Iridium version of the plug.

I put the 185 main jet in and cleaned up the plug a little. I don't have a spare new plug.

I took off and a block from home (not warmed up mind you) I opened up the throttle and it appeard to me that the engine was cutting sooner - closer to 5500RPM. So I brought the bike back and popped out the plug. It looked like more soot than when I started.

Wasn't the smaller main jet supposed to put me in a better place rather than worse?

Should I wait for the new plugs and try again on a clean fresh plug?

Thanks you guys...

Jim

[Bevel bob]

I had the same problem, cutting out at 6k, i went to smaller main,dropped needle ,changed fuel level, sorted now but no real idea what it was, keep trying!!!.

[JimF]

New plug installed, I had found the needle to be fully dropped already.

Without riding I am finding that just reving up on the driveway (no load) it's cutting out around 6200 RPM.

Kepp your ideas coming. I have one jet smaller (180) that I can put in today.

Jim

[Bevel bob]

forget the revs, what is the throttle position when it cuts?

[JimF]

It's funny you should ask that because after a more "ponderous" ride I realized my throttle position is not wide open - so I am thinking that I am not on the main jet.

I just sat down to write when I found you are a step ahead of me.

I'm going to say that I am at roughly half throttle.

Additional information:

Needle now at center (position 3.)
Main jet now at 180
Needle jet says "5F21"
Slide says "2.0"

[Bevel bob]

Sounds like needle needs a drop or a new needle jet. Best not to trust a cleaned plug,try a new one with the new setting.Top grade fuel gives my 250 indejestion.

[JimF]

A friend of mine once said '90% of all carb problems are electrical."

I looked at the points are they look awful. I pulled the points plate out and there is no centrifugal advance on this bike.

New points and for good measure a new condenser are now installed.

Forecast is for highs in the 40's tomorrow so it will be at least Tuesday before I know if the points affected the artificial rev limit.

Jim

[Bevel bob]

Fixed advance comes with the mag system ,usually, sounds like a poor option for a bike on the road,its either going to be a pig to start or not realise its potential with limited advance. Ok for a competition bike but for pleasure riding? not for me.

[JimF]

Because I dropped two sizes on the main jet from a 190 starting point, then to 185 and now to 180 with seemingly no change in the symptoms I changed the points and reset the timing.

I had a previous thread going regarding the points system which as it turns out has no automatic advance.

So rather than try to run this particular thread under two discussions, please refer to :

viewtopic.php?f=3&t=757&start=10

Thanks!

Jim