GSXR carbs

[madmax-im]

I have dyno sheets posted on the forum somewhere, but the 90bhp peak is only half the story; The bike starts, runs and drives like a far newer design; there is far more bottom-end power, and trickling along through traffic is much easier, since it pulls right from idle (and I have no first gear!)

DO IT!!

AlanB [/B][/QUOTE]
Hey Alan...just curious if you did a before dyno run and just what kind of gains you obtained...in terms of hp and torque...the other part of the above statement puzzles me somewhat...You mean to say you have noo first gear at all?You start out presumably in 2nd???Surely you could do the tranny fix..

[AlanB]

Hi Max,

My bike has never had a (reliable) first gear, but I have never found it to be a problem........ so I have never got round to doing the gear fix. I actually have an undamaged gear set in the shop, with the washer already moved; I will fit it sometime!

We did run the bike "before and after"..... it made around 70brake on the original carbs, and we hit 95 during development runs. We finally settled for a solid 90bhp with a good rounded curve...... It looked a lot better than the version with the big peak numbers.

I am sure that more dyno time would have given the best of both, but I am more than happy with the results........

AlanB

[madmax-im]

That brings up another point ...I have no clue as to where to find a shop that has a dyno in my area so without that input it will be hard to tweak the carbs for best performance???I'm not really all that knowledgeable but willing to learn.As far as working on my own bike...I am an unmigitated disaster...LOL.The assistance and/or guidance of one most knowledgeable would be of great service!

[MattWenrick]

I think Philly Cycle Center has a dyno. Only set-back is they aren't a Yamaha dealer. But I've been told they will work on anything. I've got the Cycle Stop down the street from me in Norristown, they have a dyno. Check the online phone books - searching for dyno, motorcycles

[Guy_b_g]

I'm sure I'll try both sets of carbs at some point, just to satisfy my curiosity if nothing else.

Since I'm doing the bigbore kit, with porting and heat barriier mods, at some point I'm gonna want to find out what the ultimate HP combination is. That means I have to try the RS carbs, and see if the gains are worth the driveability tradeoff.

When I had my Guzzi LeMans, it had oversize (40mm) Dellorto's, which have very similar characteristics to the RS carbs. That bike was also ported and cammed out. Once I got used to it, that bike was a fun ride. There were drawbacks. For one...I had only 2 left side carbs, and therefore could only use 1 starting circuit. It started fine firing on one cylinder though. Sounded strange as the engine oil heated up and the other cylinder gradually came to life. Had a LaFranconi stainless exhaust system on it and once running the thing sounded like it belonged on the track at a NASCAR race.

You had to be careful starting up, with accelerator pumps, a cold engine backfire thru the carbs could ignite a small fire, with puddled fuel in the carbs. I soon learned to leave the throttle alone until the engine had a bit of heat in it. Funny thing...that bike was a '78 shaftie too. Seems I've come full circle.

If I can make the bike behave with the RS carbs it'll be worth it. But if the throttle response isn't smooth enough, a shaft drive can be a handful in the corners. While the Tonti-framed Guzzi handled like a dream... I learned not to chop the throttle in a hard corner on pain of grounding a footpeg.

It'd be a shame not to at least give a set of RS carbs a try on this old horse.

[madmax-im]

Guy,it sounds like you are up to the task with trying the RS carbs...I'd be curious as to what might come of it.For me it will be extraordinary just to get the GSXR slingshots' to fit and work....so if i can do that and they work...I will be very happy!Ofc the other half of the Madmax equation is fixing the tranny....after all...what freaking good is it to ahve great throttle response and all if the tranny ain't up to par?Oh...projects...projects...

[Guy_b_g]

Thanks for the vote of confidence Max.

Gonna try it anyway...but it may end up with me being a little wiser, definately a lighter wallet, (they say 9lbs=1HP )
and maybe sorry I didn't take some good advice...but I'm just stubborn that way I suppose.

I do have to say that it feels good to have the slingshot carbs ready in case of failure.

Problem with this bike is I never seem to be able to look at it without seeing something that can be improved, or painted, or powdercoated...and this site is such a treasure trove of ideas and mods that I could just work on the bike forever and never get to ride it. Not that that's all bad...I love doing this stuff...but I'm starting to get spring fever, and trying not to rush anything to just get it on the road.

For instance, I just bought an 81 head ($29, ebay), and took it over to my friend's machine shop, and tore it down. I also have an extra torn down '78 head...comparing the two I noticed that the intake valve stem length on the 81 is shorter than the 78...they had to inset the intake valves further into the head for clearance (larger valves). The inset left a ridge all the way around the intake valves that leave them shrouded for the first several hundredths of travel...(that's gotta go..)..just unshrouding the valves will be worth some gain.

The same guy was parting out the rest of his 81, and the head was in such good shape that I bought the tranny ($49), and found that it already had the newer factory undercut dogs...so that's gotta go in.

I love this stuff..but I get so caught up in details that it seems like I'm never any closer to riding..lol.

[madmax-im]

No lack of ideas

Well Guy...it would seem true for me as well.Just being on this forum has really...I mean really... opened my eyes and wallet...LOL... to the possibilities for my machines.I am gonna get my feet wet and dive into the vast pool of yamaha zen and such and attempt to reincarnate the old Max...he's almost there....I am ready to order my factory backcut gears both gearsets...1st/4thand 2nd/5th. from www.cycle-parts.com for $490

[Guy_b_g]

Bye the way...I just noticed that you used to own a '78 XS 400...that bike was my 2nd restoration project...great little bike. I used it to thoroughly embarrass a friend of mine on the twisties (he was on a Z1) many times in the Colorado mountains.

My third basket bike was a '78 DT400...something about '78s I guess...my first street bike was a (new) '78 KZ750B2..and of course there was my '78 Guzzi Lemans,

[madmax-im]

yeah that old '78 was a fun bike...I got 70 mpg with it and i could get it to 70 mph but dont bother looking in the mirrors...LOL that bike was a vibration bandit.I could never ride for more than 50 miles on it at one time..my hands would go numb and the seat was quite tall for my 5'9''...but around town it was perfect