550 K1 Carb Help please ( Update )

[jon stead]

Is it all four spark plugs that are shooting up, or one or two? If two, is it 1 and 4 or 2 and 3?
Have you confirmed your exhaust pipes aren’t partially blocked?

[Davelu88]

Hi its all four plugs , no i have not checked exhausts for blockages but i wouldnt have thought i would have a blockage in all four pipes or maybe im just very unlucky and i have  , however i contacted Gerben as these were a set of his carbs and he politely replied stating that the 087A carbs should have a 38 slow jet & these have a 40 in them so would that be enough to cause the over richness

[K2-K6]

I may have to go back and check figures, but I've got the 38 jet at 15.38% less area than the 40 jet.

So flow should be a noticeable difference to jetting.

When you adjust slow speed jetting and get no/little response in "normal " screwdriver adjustment range, then it is suggesting that the engine is "asking" for a different jet size to bring it within normal operating settings.

It does look like it needs the smaller jets.

[Davelu88]

Thanks K2 

[Davelu88]

Definately says stock is 38 on these carbs , Question is how much difference would this make ?

Cheers

[Davelu88]

yes i believe the pipes do go to the bottom of airbox , , after googling 087A carb specs it states 38 slow jet i have also messaged Gerben who built the carbs and he agrees that these carbs have a 38 slow jet , & looking on CMSL site the K1 & K2 both have 38 jets although the 500 does have 40 , so not sure why the 550 has a smaller jet.

[deltarider]

You can replace the slow jets with carbs in situ. Allen screws make it easier to remove the bowls.

[Davelu88]

Have ordered 38 jets will let you know if any difference is made 

[deltarider]

Have ordered 38 jets will let you know if any difference is made 

Looking forward to that. I have always wondered if it really makes a big difference.

[Davelu88]

Just a quick update on my carb issue , the 40 jets have been changed to 38 carbs balanced etc & it seems to idle , run ,accelerate ok , did a chop test on plugs and although a bit sooty they are nothing like they were so fingers crossed all ok . Many thanks for all the help on here.
Cheers Dave

[Raymond_Y]

Where did you get your #38 slow jets from?

Raymond

[Davelu88]

Got them from Dave Silvers, have to special order them & took about a week to arrive £30 for the 4 of them . part number  991240760380

[Bryanj]

Try Sirius in Canada

[deltarider]

Or CMSNL in The Netherlands. https://www.cmsnl.com/products/jet-slow-38_991240760380/#.XKUPJ9hcJVc

[K2-K6]

Sounds like a positive step towards optimum.

Longer running and more through heat range may see the plugs a bit better colour as it's used more.

Maybe it'll respond to airscrew tweak if not.