Jetting

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Paul

Jetting

#1 Post by Paul » Tue Jun 07, 2005 11:37 pm

G'day everyone, i need your help.<p>Before i melt down my new motor again i would like to get some advise on jetting.<p>I'm running TSI mods on the motor, Jolly Moto pipes, 28mm Mikuni's with pod filters on the carbs, TDR Reeds.<p>Can someone recommend carb set up for me that will get me close. Pilot and main jet size and needle position. I want to get as close as i can before fine tuning on a dyno.<p>It's not running real well at the moment, real rich. Used a tank of gas for about 100km's.<br>Real sluggish to 5000rpm, not to bad to 8000 and then starts breaking down again. Like riding with the choke on.<p>Not sure of the current jetting. The Carbs were off a stock RG500 and i'm told the jetting suited that.<p>Thanks in advance<br>Paul<br>
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paulwfreund@hotmail.com

Rick Lance

Re: Jetting

#2 Post by Rick Lance » Wed Jun 08, 2005 3:28 am

Hey, Paul!<br>Well, you asked for help. I just hope that you can put this to good use.<p>Ditch the RG carbs. There is no correct setting for these carbs on your motor. Take a look at the needles from the stock RZ carbs and the Gamma ones. They are polar opposites of each other. The RG has rotary valve induction with an ATAC style power valve. The RZ has reeds and YPVS. Your TSI motor mods raise the question of whether the motor can EVER run right, no matter what carbs are used, much less jetting. The TSI specs were written 20 years ago for competition use only with rapid parts replacement and no concern for part throttle drive ability. Most tuners are embarrassed by what they did 20 years ago, compared to where they are now. I am sure that the Yamaha tech

Wyn Belorusky

Re: Jetting

#3 Post by Wyn Belorusky » Wed Jun 08, 2005 4:48 am

Rick - how are the Gamma 28mm flat slides different than a new 28mm flat slide that can be bought from Mikuni?
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RZVWyn@aol.com

Rick Lance

Re: Jetting

#4 Post by Rick Lance » Wed Jun 08, 2005 3:02 pm

Hey, Wyn!<p>The RG carbs were designed by Suzuki for the Gamma. They have very shallow float bowls to clear the mag cover which cause starvation when jetted for open filters. The stock main was a 120. The main climbs to the mid 200's without the stock airbox. The needle is a very flat taper quite unlike any aftermarket Mikuni part. The carbs are a flange mount rather than a spigot type. The main air jet is pressed in, not threaded and tunable. The RG carbs were optimized for use with rotary valves (strong intake signal with no restriction) rather than reeds (shorter intake timing with energy loss opening reed valves). Aftermarket Mikuni carbs are set up expecting something similar to the RZ500 needs. The RG carbs were not. The Gamma carbs had what Suzuki called SAPC which was a tube connecting the front and rear carb venturis together for better part throttle behavior, somewhat like the RZ's balance tube from right to left. Having both systems present and active would have all carbs connected with pulse waves galore bouncing everywhere. I'd rather run stock RZ carbs.<p>Rick
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rick@lancegamma.com

Wyn Belorusky

Re: Jetting

#5 Post by Wyn Belorusky » Wed Jun 08, 2005 3:08 pm

Rick - ok, sounds like Gamma Mikuni's are not the hot ticket. I can tell you that "normal" 28 flat slides from Mikuni work real well on the Yamaha, real good. Better than anything that can be done to the stock Yamaha carbs.
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RZVWyn@aol.com

Paul

Re: Jetting

#6 Post by Paul » Wed Jun 08, 2005 5:03 pm

Rick,<p>thanks for the info, who would have thought the Mikuni made 28mm flatslides for the RG500 and then something completely different for everyone else. My engine builder specialises in rebuilding RG500 motors for speedway so he had a heap of spare carbs laying around and i got some pretty much for nothing.<br>Guess i'll have to get some of the "other" ones.<br>I'm heading off for work again shortly so i'll be away 5 months which will give me time to get it sorted. <br>A lot of time went into making up all the cables, will these still fit up alright with non RG carbs?<p>Thanks Paul
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paulwfreund@hotmail.com

Rob

Re: Jetting

#7 Post by Rob » Wed Jun 08, 2005 5:55 pm

Jets are changeable, and you can buy new float bowls from Sudco. Question is... is it cheaper to go that route than to buy new ones?<p>What other bikes out there used 28mm flatslides?<br>
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motorhead9876@yahoo.com

Wyn Belorusky

Re: Jetting

#8 Post by Wyn Belorusky » Wed Jun 08, 2005 7:19 pm

"What other bikes out there used 28mm flatslides?"<p>I know the Suzuki RM 80 uses it.<p>I bought mine new about 5 years ago and then they cost about $125 each.
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RZVWyn@aol.com

Clint in Australia

Re: Jetting

#9 Post by Clint in Australia » Thu Jun 09, 2005 1:33 am

I bought 28 mm Flatslides off an RG250, Same as you buy aftermarket not flat mounted as the 500 ones are.<p><br>Rick do you think these are the better option?<br>
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clintsanders@dodo.com.au

Rick Lance

Re: Jetting

#10 Post by Rick Lance » Thu Jun 09, 2005 3:53 am

The RG250 was reed valve and should be more compatable although aftermarket Mikuni would probably be best. OEM carbs can have some odd things engineered into them that may not be apparent, such as the convoluted main air jet circut on the stock RZ. Rather than breathing from the airbox, the main air jet gets fed from the float bowl vent. On a standard Mikuni vm26 carb, it would be open to the airbox. OEM application carbs are designed by the bike manufacturer and contracted to Mikuni or Keihin for production. The OEMs will take liberties with design to compensate for specific oddities in the total package such as pipe or airbox needs that pop up. Their solutions may not be compatable with another application.<p>Rick
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rick@lancegamma.com

Mark Holmberg

Re: Jetting

#11 Post by Mark Holmberg » Thu Jun 09, 2005 4:05 am

Rick,<p>Could you elaborate a bit about your critisism of the TSI-Specs?<br>My cylinders and heads are modified as described in the TSI, + Jollymoto pipes + a lot of time spent rejetting. My bike has excellent part throttle behaviour, it makes noticeably less power below 3000 rpm, from there to 6000 I'd guess the same as std and above that nice big increase (it feels more "2-strokey" than before). <br>Some years ago I got the chance to ride a race-only TSI modified RD, complete mod incl. pipes + VM36 carbs, Dymag 17" wheels etc.etc...and there was nothing hieroglyphical about that bike, in just a few words; It was the fastest bike i have ever riden during my 24 years of riding bikes, and it wasn't half as bad as you describe.<br>So with that in mind, and that i have seen some other negative comments about the TSI specs, what would be a better solution for our ancient bikes, where are the solutions?<br>We are handicaped by tiny 70's reeds, the weirdest intake combo in biking history, almost no room for transfers, how can "modern" science work around those bits.<p>Where are the solutions? I have never seen anything suposedly better posted anywhere, and would love to see a modern aproach to getting more power out of these bikes.
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bikeboy500@gmail.com

wolfgang

Re: Jetting

#12 Post by wolfgang » Thu Jun 09, 2005 8:35 am

Does anybody have experience with KEIHIN PWK28 carbs? They are "Half-flat" slide, i.e. one side flat, the other one round.<br>My engine guru from germany favours them, I haven

Jeff B

Re: Jetting

#13 Post by Jeff B » Thu Jun 09, 2005 12:49 pm

I looked into them a little, but decided on the flatslide mikuni's mainly because there are a lot more people here that have experience setting them up for the RZ500 than the Keihin carbs.
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beeks81@aol.com

Eric

Re: Jetting

#14 Post by Eric » Fri Jun 10, 2005 4:29 pm

Paul,<br>You should check with Doug at Motocarrera.com, he seems to have about the best price on the TM-28's as far as the USA market goes anyway. I think they are running about $105 each, give or take a buck or two.<p>BTW, I've just got to ask. Weren't you just the slightest bit curious after having the rg500 carbs in your hands and seeing the flat flange type mounting surface on them as to how you would mount these carbs to the intake boots on your rz500 engine? <p>Eric <p>
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rzv500r@aol.com

Paul

Re: Jetting

#15 Post by Paul » Fri Jun 10, 2005 5:56 pm

Hi Eric,<p>yeah the flat flange made for some extra work, had to make up some spigots to mount them up. I just assumed that everyone was doing this. Do you have a Mukuni part number for the 28's i should be using. Don't want to get parts all the way over from the US and get the wrong ones. That price is pretty good i'm sure i priced them new here in Australia a while back and they were about double that.
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paulwfreund@hotmail.com

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