851/S4RS pics

marvin

Another Forum member has informed me that some of the pics I posted of my '92 851/S4RS engine swap have been deleted so here they are again.

dudlington

Exhaust

I am currently building a deep sump 1038cc engine into an 888 and would like some more information on your exhaust. I have at present 57mm Titanium headers running along the LH side and out the back of the rear cylinder. What I need help is with the optimum lengths required and do I need to add some balancer pipes between ?. More photos or sizes would be greatly appreciated.

marvin

dudlington wroteI am currently building a deep sump 1038cc engine into an 888 and would like some more information on your exhaust. I have at present 57mm Titanium headers running along the LH side and out the back of the rear cylinder. What I need help is with the optimum lengths required and do I need to add some balancer pipes between ?. More photos or sizes would be greatly appreciated.

I used 50mm stainless. I just looked at 888 spaghetti systems and sort of copied them. I did no calculations so I am of no help to you, sorry. You will have a hard time getting a 57mm pipe to clear the swingarm I'm afraid!

Here is a link to a discussion about balance pipes by people who know a lot more about exhaust systems than I do.

dudlington

Exhaust

Thanks for the reply. Basically I am using a swinging arm/Ohlins front end/wheels/brakes etc from a 999S from 2003. Using the swinging arm means I can have the 57mm system running out the back cylinder, curving around, under and out the RH side ala 888. What I will do is as you say try and copy as much as I can from the 888 race systems I have seen. Currently my engine is quite heavily modified (approx 170 Hp ) but I do not want to waste too much with my home made exhaust system. I am quite happy to cut/weld the Titanium system but need some help with lengths and the balancers.

Mr.R

170 rwbhp in a 851/888 chassis are you mad or just building a drag race bike???
The factory found the limits of this frame/rolling chassis at around 136 rwbhp, which's why the 916/955cc race bikes were built.
Are you familiar with the term "Flexi Flier"?
This term/name was coined for the mid 70's TR750 Race Suzuki's, but was also very apt for the Kawasaki Triples of the day.
Because they had waaaay too much power for their frames/rolling chassis.

Steve R

dudlington

Concern

Steve

I already have an 888 frame machine (Albiet with a 999S engine fitted) chucking out 157rwhp(More than 170 Hp at the crank) that has been extensively raced with no known problems. The 1036cc will give similar HP but I am hoping for more torque from the longer stroke as I want to use it for the road. There are fairly competitive 888 frame machines out there being raced with 1098cc engines with close to 200Hp at the crank showing the frame design to have been basically ahead of its time. A little flex is not such a bad thing

Mr.R

Fair enough, the 916 era chassis was developed to calm down the handling and eliminate the crankcase cracking problems.
I've ridden bikes where the motor's power far outstripped the chassis capabilities and it wasn't fun.
It's your neck chap crack on...

Steve R

BARONROJO

Thank you very much for the pics, marvin.

When I finally go back home, I'll try to make an extensive topic about my 851/ST4s constructions for everyone interested. I think it's really the kind of quality info not very often found on the internet.

These pictures are of great help! 😎

hauge

Nice project Marvin!
Did the s4rs engine have the same ugly arangement for the cooling hosese as the 999?

marvin

hauge wroteNice project Marvin! Did the s4rs engine have the same ugly arangement for the cooling hosese as the 999?

Not quite as ugly. I don't remember exactly what I used but mostly from the S4RS and maybe some ST4 parts. Still not "pretty'!

Mr.R

Marvin,
Did you ever put it on a dyno and if so how much was it making?
Also thanks for posting the pic's again I'd forgotten how nice/neat your project was/is, could you post pic's of the HUGE catch tank/breather box that you built please?
I'm thinking of fitting something similar to fill the space under the seat hump on my 851/916cc bike, but it's more for the 955cc motor.

Steve R

marvin

Hi Steve,

I will when I get a free moment.

Mr.R

Cheers Marvin that would be great mate. 😎

Steve R

Mr.R

marvin wroteNot quite as ugly. I don't remember exactly what I used but mostly from the S4RS and maybe some ST4 parts. Still not "pretty'!

That's what the fairing's for mate, 😉 it hides a lot of ugly parts/a true plumbers nightmare.
Lets face it here a naked 851/888, with no mater what Desmoquatro motor's fitted is never going to look as handsome/pretty as a round or square case 750/900SS Bevel, DBD34 Goldstar, or Manx Norton motor.
When the full fairings came in the Italians stopped casting up works of art...
Having said that the Desmoquatro motors look a whole lot prettier than any V twin motor that Aprilia have come up with so far.

Steve R

marvin

breather box

Steve, Here are some pics of the breather box and airbox. The color is off, too lazy to change the settings on my camera to fluorescent. I glued up a block of the blue insulation foam and covered it with fiberglass cloth and epoxy resin. Then poured gasoline, lacquer thinner, acetone, etc. in it to dissolve the foam (what a mess, next time would use the white light stuff) I also glued in place a stainless screen to separate the oil better. Used the stock reed valve and a small filter. It is ugly and was made to clear the old relays of the stock engine. The next one I make will probably be out of welded aluminum sheet.
The airbox was made of aluminum sheet. I didn't have much luck grafting the stock airbox to the S4RS airbox. I wanted to use the stock upper cross brace (made ends so I could remove it). Using an 888 frame/airbox would be much easier (without the cross brace).

marvin

P.S.

Steve,

No I have not taken it to the dyno yet. I have to burn a better chip first. I have a dual channel Innovate LM-2 data logger and bungs welded in the exhaust but never get around to it. It runs well except if you hold it at about 7K where it sputters. If you nail it, it runs right through that range so I'm guessing it's a little lean there and when you hit it the ECU delivers extra fuel in that range. One of these days!