Main jet size

[badlydamaged]

Hey there, I have decided that my last crash wasn't spectacular enough so I am looking to give myself a bit more power from my bike (basically derestricting it).
I have been told that the restriction on my Kh100 is the carburettor.
I know that the pre restriction kh100s were always fitted with the same carburettor as my restricted one and after doing some research on the differences of pre restricted and restricted bikes teh only difference I can see is that the main jet size on the later bikes was smaller than the one of the pre restricted bikes. Therefore I figure this must be the restriction. So If I change my main jet to the same as the pre restricted bikes will I unleesh that tiny little bit more power? I always thought that the main jet just affected the mixture and putting a small one in a carburettor would just cause the engine to run week (and the only way to uprate the carburettor would be to increase the diameter of the bore)
Basically all I need to know is will changing the main jet size give me more power if the bike has been jetted down to restrict it. Im not expecting any large change in power (only 1hp or so) but it would be so cheap to do that any power increase, however small is worth it imo. Changing the carburettor itself to a beefier one will make a larger difference I know, but im not looking to spend money on making it go faster, as its just not worth it on my bike. OR have I got the wrong end of the stick and messing with the jetting will just make the bike run rich and the restriction must be somwhere else?

I know this is a really boring question, but I really would appreciate it if someone could point me in the right dircetion with regard to this. It would be much appreciated
By the way the way the carburettor specs are below, the KH100 EL being the pre restricted bikes.
____________________
My bike: 1988 Kawasaki KH100 Status: Polluting Devon with two stroke smog and noise pollution!
"Its not your engine size that matters!, It's what you do with it that counts"
Add me to MSN if you want! badlydamaged@hotmail.com.

[Kickstart]

Hi

Suspect there is a difference somewhere else. Either in the exhaust or probably more likely in the disk valve. Suspect the main jet is just to compensate for that.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[badlydamaged]

Thanks very much for your reply m8 I was thinking that may be the case with it, Ive had the exhaust apart to decoke it in the past and didn't see any obvious restrctions. Wouldn't know where to start with the rotary disc valve, thats definatly something I don't want to go fiddling with on my own. Ive had a few people say that the main jet could quite likelly be made smaller to decrease power out put, but to me it sounds more like what you said, something to compensate the reduced flow of air into the engine caused by the restrictors. Il rack my local bike mechanics brains on it next time I see him, other than that all I can do is test it with different sized jets in.
Thanks again for your help, was hoping you would reply as you know your stuff!
Cheers, Jonathan
____________________
My bike: 1988 Kawasaki KH100 Status: Polluting Devon with two stroke smog and noise pollution!
"Its not your engine size that matters!, It's what you do with it that counts"
Add me to MSN if you want! badlydamaged@hotmail.com.

[Kickstart]

Hi

Trouble with just reducing the main jet size on a 2 stroke is that you will land up running the risk of seizing.

I would suspect an earlier disk valve will not cost that much.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[badlydamaged]

Hey again, Ive just read in an old issue of Used Bike Guide in the review for the kh 100: "......Restricted by 19mm carb; increase to 22/24mm for extra go!(rememeber its illegal to sell to a learner in that condition though)" Someting else which suggests the carb is the restriction although this refers to the barrel size than the main jet.

The reason I asked about this on here was because I thought it was unlikely that a bike manuafacteur would limit the performance of their bikes by down jetting with the risk of the bike overheating and seizing due to the lean mixture it creates unless the airflow is also restricted, by the exhaust or otherwise. I thought it was more likelly a smaller carb would have been just wacked on instead, however all sources say (including my ancient 1977 pre restricted service manual) that Kh100's have always been fitted with the 19mm carb.

I think the best soution would be to test it with the slightly bigger jet that the pre restricted bikes were fitted with apparantly, its cheap and easy so I have nout to loose. But first il have a quick word with my local bike mechanic about it.

Thanks again for your help, im going to look into all these things before I go taking my carburettor apart, and will ask about the likellyhood of a restrictor in the rotary disc valve as you have suggested.
Cheers
____________________
My bike: 1988 Kawasaki KH100 Status: Polluting Devon with two stroke smog and noise pollution!
"Its not your engine size that matters!, It's what you do with it that counts"
Add me to MSN if you want! badlydamaged@hotmail.com.