I have just installed a 2009 motor in my son's04. Prior to doing this I ordered a jet kit for the 04. The 2009 motor was a complete motor with all wiring etc and carb's.

The new motor runs well; it is smooth idling etc.

The question is do I re jet or leave it alone until I run into issues?

Some advice please?

The biggest advantage to going up a size on jets is the low rpm usability.  Many owners are perfectly happy with stock jetting, and the longish warm up time and lack of power under 3-4k rpm. I also hear that there is some leaning out at 5000 rpm with part throttle. That would bother me...

My bike is far from stock, but I like being able to begin slipping the clutch at 1500 and fully engage at 2000 and throttle on out.

Thanks, so in your opinion, it more personal preference rather than improvements in performance or driveability. This bike is for my son and wife to share; they are fairly new to the sport so all we want is reliable and easy to ride etc.

Thanks,

Yeah, one of the biggest things that drove me nuts was that if I was accelerating normally then there seemed to be almost no power available around 5k.

I'll just repeat what I always say on this subject, DON'T MESS WITH YOUR CARBS AND THEY WON'T MESS WITH YOU!  Only exception I can see as worthwhile would be when modding a GS with exhaust changes a rejetting would be desirable as with most carburated bikes.

I've never touched the carbs on either my 97 or 02 bikes in the 170k total miles I put on them, both engines remained completely stock.  Riding year around here in NE Ohio in temps down to 20F I found the 97 with the old 2 circuit carbs to be too lean for winter use but I had an old CM400A I used winters then.  I've used my stock 02 year around and it doesn't need any rejetting for winter use with it's newer 3 circuit carbs.

Thanks Jack, I was leaning towards leaving well enough alone, the engine is running well enough for the users that are using it, so the performance is spot on. So having said that, I will keep the jet kit in the tool box.

Again, thanks for the advice

I would tend to agree with leaving well enough alone unless you do some other modification that requires a rejet (exhaust or air filter).  I did do a rejet on my bike after doing both and I do love the difference and has not caused me any problems/adjustments since I did it.  If you are looking for a good father/son project it might be a good one as you get to learn more about the bike (if you are interested in thatl).  If you are just looking not to change anything and just ride then leave well enough alone

Thanks

Quote from: merlinq21 on June 20, 2012, 07:53:57 AM
Thanks Jack, I was leaning towards leaving well enough alone, the engine is running well enough for the users that are using it, so the performance is spot on. So having said that, I will keep the jet kit in the tool box.

Again, thanks for the advice

In my experience, jetting has caused a few problems.  Notably:

• I didn't get the jetting correct the first time.  Had to start again.
• Fuel economy dropped.  I get 20-25 less miles to the tank.
• Choke inconsistencies when I need to start the bike cold.  Sometimes I need it, other times I don't.
• Re-routing of vent hoses after I got rid of my airbox caused headaches until I figured out my problem.  Search "Crosswind Engine Stumble"

Having said that, I am a tinkerer.  I futz with it until it breaks, then correct.  That's how I learn.

YMMV, however.

thanks, tinkering cost me a new motor, so no more of that. I will stay as is, no need to futz with it right now.

Carbs receive too much mystical credit on this forum.

It's not the space shuttle.  It's how the gas gets into the engine. 

If you switched out a motor, you absolutely have the mechanical ability to rejet a carb.

*disclaimer, I haven't rejetted my gs, but I've been inside carbs before on other bikes and atvs.  but still. go for it.

Thanks,

I agreed on the re and re skills, however, not sure that the time I will invest in re-jetting will bear any noticeable results for two newby riders- last year they were on a CBR 125- so as the bike sits it more than enough for my son and wife.

Main mission is to have a ride able bike for them, they need more seat time and confidence. So unless I find a compelling need to futz, the carbs shall stay sealed and the bike will be cared for.

I am sure the bike will be sold with in the next two years- my son is off to university this fall so when he gets back I am sure we will be on a hunt for a bigger unit.

Thanks again- GSjack has never had to jet his bike, that to me is enough to just leave the carbs alone.