KR-1S.co.uk Forum

Bike came with 137.5 jets that were marked RD underneath the sizing so I assume are Yamaha. Needle circlips were in centre slot.
Other set of jets I have are 130's from another donor KR1.

Std according to the online manual is 135 I think.
Advice as where to start might be useful in the extreme!!!
Bike is an 1989 KR1.
Has it been breathed on internally? I expect so but haven't ripped it down to find out yet!!!!

nobody knows their setting eh?



Must be a KR Forum secret squirrel thing then!!!

Only real way of setting them up properly is to get it on a rolling road, where abouts are you located

Maidstone, Kent.
Spoken with Taymar Racing and can get a slot on theirs................ in November!!! Yeah, Martin's a busy boy.

This is just for me to get a rideable KR1. I'm not looking for ultimate power (well not that much LOL) just useability. Sure it can be done or maybe I lob in the spare engine that goes OK???????
I didn't ride that engine but my mate did (racer) and said it went OK.
LSM

Since no engines are the same, there isn't a general rule for jet-sizes .

How does it run now ? if you tell us where the problems are, we can direct you in the right way.

if it runs right as is and you have std airbox/pipes/filter in place etc i would imagine your bike is jetted close enough to be safe from seizure. if in doubt, put the clip in the middle groove, fit std 135 mains and see how it is. also start at the rich end (bigger jets) and work down. theres a few jets that can be used in pwk 28mm carbs. i dont think the RD has any relation to yamaha, just a type of jet. if the bike is pulling cleanly etc on warm days, then it could well be on the lean side in cooler days/evenings etc so just tone it down if in doubt. best thing to do is bang in some 135's/middle clip till you visit the dyno armed with jets etc.

the RD is the manufacturer, they are an aftermarket jet and not made by Kiehlin IIRC

MGTKR1

It doesn't pull cleanly cold or hot!!! Bike is all airboxed std with a foam Piper X filter.
I will have a play and see what gives.
Anyone recommend a place to buy 135 jets?

LotusSevenMan wrote:MGTKR1

It doesn't pull cleanly cold or hot!!! Bike is all airboxed std with a foam Piper X filter.
I will have a play and see what gives.
Anyone recommend a place to buy 135 jets?

any bike shop should be able do deliver them .

are the chokes seating properly/adjusted right?

wouldn't think main jets have much influence on general running until
big throttle openings

are the powervalves set correctly?

Well it's difficult to know what is 'correct' but the choke plungers are shutting off OK.
Powervalves (to my limited knowledge) are set OK. They open and shut!!!!
I'm sure it's a jet/needle thing as when the bike gets to 9,000 it absolutely takes off. Clean, cleared out and it clears off down the road no problem.
It is just 'woofly' lower down and won't pull through very well to the powerband. It's more a case of struggling to get enough revs to then be able to knock it down a couple of gears to get it on the boil.
Can't hold fifth or sixth on a dual carriageway run as it doesn't have the revs.
The bike is better with the 130's without the mega jump in power that it had with the 137.5's but a little more friendly in midrange.
This bike has without doubt been used for racing/track day thrashing so with the original set-up it would be fine as a peaky 'racer'. Not good for std road use ya see.

If its running well at the top of the revs then it isn't the main jet as these only comeinto play above 9K or 3/4 throttle openings. I would look at your pilot jets, and the needles.

Just a thought are the float levels set correct? it's not "flooding " is it? also check that the carb mounting rubbers are tight "the two jubile clips that hold the carburetor's in place" I had a simalar problem once, & I had forgoten to tighten them up

Thanks Elf.
Needles in the clips? OK, play time (once weather gets better. Bl%dy raining again here in Kent) !!!

Check for a blocked pilot jet, worn needles and slides, and air leaks etc.