Need a little help in the right direction...

fastkart · Post by **fastkart** » May 3rd, 2008, 10:24 pm

Got my GSS motor to the track today for the first time after a month of waiting due to all the frickin' rain we've been getting in Iowa.

Got the motor warmed up... it will be happy to run all day sitting still, either in gear with the clutch pulled or out of hear, with just a touch of throttle to keep it running and the occaisional blip to clear it out some. When I was idling around the track lining up to race, it would rev out just fine with the clutch pulled. The moment I release the clutch, hit the throttle and put a load on the motor it does nothing but sputter and surge some, and not go at all at WOT. It was jetted pretty rich, so I leaned it out... went from a 200 main to a 190, and from a 120 to a 115 in the powerjet. Changed the plug while I was at it. It made no difference on the track, same symptoms as before, but the plug was definately not nearly as wet, and was almost dry. I had a spare set of reeds (boyesen cf stockers, per Glen's suggestion were in the motor, changed to a brand new vforce setup). This made no difference either, the motor still acts the same.

The top end was all brand new before I sent it to Glen for a full race port job. The bottom end is all fresh... brand new crank, all new oem bearings/seals, etc. I'm running C12 mixed 32:1 with Blendzall, and the fuel is fresh (2 days out of the pail). My fuel filter is next to new, as is the fuel pump so I have no real reason to suspect either of those. I also don't really have reason to suspect the carb. It's clean as a whistle, and was ran last year doing the same thing I am now, and performed flawlessly. The only change is the powerjet kit that I had Glen install.

I'm pretty sure I've got my bases covered, just looking for some advice before I really rip into it and give Glen a call on Monday for his thoughts. I just find it odd that out of gear or with the clutch pulled it will rev just fine, but not at all with a load on the motor.

britincali · Post by **britincali** » May 3rd, 2008, 11:15 pm

Go leaner on the main.

fastkart · Post by **fastkart** » May 3rd, 2008, 11:20 pm

I was thinking that, Glens suggestion was leaner, like a 185 or so but it was also pretty cold... 45-50, so I was trying to play it safe. I should have seen a difference between the 200 and 190, shouldn't I?

britincali · Post by **britincali** » May 3rd, 2008, 11:25 pm

Not if its rich as hell.

I run a 172 in my AF and a 178 in the GSS bike.

fastkart · Post by **fastkart** » May 3rd, 2008, 11:33 pm

Hmmm... ok. Glen was saying to run something like a 185 in the main, and he put a 120 in the mikuni powerjet setup he installed. I guess I thought I would be in the ballpark with what I've got now.

dannygraves · Post by **dannygraves** » May 4th, 2008, 10:46 am

you should decrease your main size by %20 with a powerjet. my bike runs like a MOFO and I just have an 80 mikuni powerjet and a 340 main jet (which should equate to around 150 in keihin numbers) drop that main a lot.
the trick to tuning a powerjet, is if you snap the throttle, or hold it for a split sec and it runs great, then your main is ok. If it sucks under load when you snap it all the way open, your main needs to be changed. if the main is ok, but you hold it open for extended periods, and then it starts to run crappy, then its time to work on the power jet. you should feel when the powerjet kicks in, just feel the mixture changing slightly.
much leaner on that main dude.

Post by **AlisoBob** » May 4th, 2008, 1:49 pm

To my knowlage, the powerjet is added to tune the bike with... without pulling the floatbowl all the time.

Example:

If the bike runs good with a 180 main.... install a 165main and tune the powerjet.

Then, you can effectivly run anywhere from a 165 to 200 without touching the floatbowl...

Having a 200 main + the fuel from the powerjet makes no sense to me.

fastkart · Post by **fastkart** » May 4th, 2008, 3:30 pm

AlisoBob wrote: Having a 200 main + the fuel from the powerjet makes no sense to me.

Agreed. However, Glen was recommending something in that area for jetting, so I went with it, knowing that Glen knows whats going on with a 500. I had a feeling it was running rich... thats alot of fuel. Again, I was on the rich side (it was sorta cold) of what Glen suggested as a starting point, which to me means it should be somewhat close, but not perfect. Thats why I didn't lean it out any further than I did.

DG- I know it's not your motor, etc, but when you suggest I drop the main alot, what are you suggesting? 160ish to start with or further yet? I have no clue what it would run without the powerjet, aside from what Brit said. I like to play it somewhat conservative. Changing motors at the track is a PITA.

Next race is Friday night. We'll see how it stacks up to the competition then.

PS- Not blaming/whining/whatever about the issue or Glens suggestion. It's possible I misunderstood what he was saying. S%*! happens. Glad it is only jetting.

dannygraves · Post by **dannygraves** » May 4th, 2008, 4:50 pm

ya, 160-ish sounds good and a little rich for a powerjet setup. remember, the powerjet is your extended WOT insurance, not the main, the main just has to keep it running good when the slide is snapped open, after its held for a while and a vacuum is created between the slide and the airbox, then the powerjet will start to flow. when I first put my setup together, I was running a 420 main and 120 power... it ran like snot. I did the math and dropped the main to like 340 and then it ran great when the throttle was snapped open, but blubbered after a second. I tried 100 and ended up at 80. it runs like a bad mofo now.
I would bet you will need to go a lot leaner than 160, but you want to take things in steps. 200-%20=160... makes it a good starting point. form there you will probably have to lean out that power jet a little. did yuou get the other jets with it?
also in the mikunis, 420 is the '01 cr250 stock size, just to give you a comparison idea.

dannygraves · Post by **dannygraves** » May 4th, 2008, 4:51 pm

my motor on a 39.5pwk w/o powerjet ran 182-188, to give you an idea.

fastkart · Post by **fastkart** » May 4th, 2008, 5:03 pm

Thanks a ton. I always do take jetting in steps... I don't need another custom made Wiseco parts dish. I got a 120, 100 and 80 with the kit if I remember right and also bought some inbetween jets at a local dealer so I have a decent selection of them to get it jetted pretty close. I know I have what I need, just didn't know quite where to start. I've had them blubber and run like crap from being rich before, but never to this extent.

100hp honda · Post by **100hp honda** » May 4th, 2008, 10:52 pm

im curious why the powerjet. only so much gasoline can be put in there effectivaly. just wondering but did somebody recomend a mikuni?

dannygraves · Post by **dannygraves** » May 5th, 2008, 7:07 am

The powerjet allows you to hold it WOT forever without it going lean. a standard main jet gives everything its got right when you open that sucker, so if you make it rich enough to handle a long period of WOT, it will run like snot right when you crack it open. They normally use powerjets on sleds since snow mobile are held WOT for long ass periods.
the powerjet if added to the carb housing between the slide and airbox, when a vacuum is craeted in this area, the powerjet will supply additional fuel.
He has a keihin PWK with the mikuni powerjet kit on it. I have the same kit on a mikuni TM pro41 carb (BTW, I LOVE this carb!). The thing I think is funny is since I got into 500s, people have been saying negative things about the mikunis. Mine performs better all over than my PWK. I had some tuning issues at first, but that was because I was running the wrong slide, and didn't hjave any real needle specs to get a base line. It runs tits now

fastkart · Post by **fastkart** » May 5th, 2008, 7:16 am

dannygraves wrote:The powerjet allows you to hold it WOT forever without it going lean

Yep. Glen mentioned putting one in because WOT racing is about all I do. I had picked up a mikuni kit but hadn't done anything with it, so I sent it and my carb along when he did the top end.

100hp honda · Post by **100hp honda** » May 5th, 2008, 8:11 am

i didnt say anything negative about mikuni, i just asked WHY

. seems like these adjustable powerjets would make lfe alot easier with tuning

dannygraves · Post by **dannygraves** » May 5th, 2008, 8:31 am

yeah, those are nice, I just worry about someone messing with it, on maybe making more adjustment then needed, etc. I like having the jets in there, its more work to get dialed in, but after that I leave it the hell alone

fastkart · Post by **fastkart** » May 6th, 2008, 8:17 pm

I just got thru putting a 155 in the main and a 100 in the powerjet. According to the calculations, I'll have to go buy some leaner mains tomorrow to be in the right spot. Its gotta run like a mofo Friday, my biggest sponsor will be in attendance.

dannygraves · Post by **dannygraves** » May 7th, 2008, 7:11 am

sounds good, now don't forget what I said about how to tell if your main or the powerjet need adjustment... if right when it opens it blubbers, then leaner main, if you hold it for a sec. and then it blubbers, then its the power jet.

fastkart · Post by **fastkart** » May 7th, 2008, 7:18 am

Yep, we're on the same page there. I just didn't envision being that far off on the jetting. I'm sure it'll still blubber, but it ought to atleast run now that I'm in the ballpark.

dannygraves · Post by **dannygraves** » May 7th, 2008, 7:20 am

I'm not at all surprised, that powerjet is pumping a lot more fuel in there. when you get it all dialed in, it will have some serious throttle response!!

fastkart · Post by **fastkart** » May 9th, 2008, 10:21 pm

I got it running pretty close with a 148 main and a 90 powerjet. Motor was fast until each and every spring holding the header to the cylinder and header to the pipe came off causing the header to get crunched into a ball by other cars. Got my spare put on with about 3 miles of safety wire only to have the rear sprocket break while running really well. One of those nights. Anyways, thanks again for the help.

dannygraves · Post by **dannygraves** » May 10th, 2008, 9:03 am

hey, when your breaking sprockets...it must me running really well!

fastkart · Post by **fastkart** » May 10th, 2008, 6:53 pm

Yeah true. I blame the sprocket breakage on the track being rougher than an effing cob. When you're in a kart without suspension and you see 3" of daylight underneath the wheels of the car infront of you from bouncing, you know its rough. The sucky parts are: this was my luck all last year. I'm considering having the local priest perform an exorcism on the car/motor/all my stuff. And 2... I have to take the GSS motor off and put on the one the sponsor bought now that I have it tuned.

dannygraves · Post by **dannygraves** » May 10th, 2008, 7:09 pm

what kind of motor did the sponsor get?

fastkart · Post by **fastkart** » May 10th, 2008, 8:10 pm

It's a CR500 as well. Thats what my class of cars runs... either that or a KX500, and a few guys have tried CRF450's.. I'm sure you know how that worked out... when they weren't being ran over they were too busy sucking valves.

The sponsors motor is built buy the guy who is known for building the best engines for what I'm doing (George Becker, in nor cal), and was his son's motor. It's an 86, with a PVL ignition (thats why I was asking about it a month or so ago), bored .5mm over, and nikasilled, and a billet clutch. It's supposed to be absolutely trick. I've ran it once in practice and it felt pretty good, but was running rich. Once its top end time I will get a good look at the porting, but from looking in the intake and exhaust the port work is completely different than Glens. I know it'll be fast because of where it came from, and knowing what I have sitting on the trailer to bolt on is nothing but confidence.

BannedCR500Riders.com

Need a little help in the right direction...

Need a little help in the right direction...