Yamaha Superjet Bigbore?????

[Exile]

What are all the parts I need to bigbore my liited superjet to 85.5mm?????
I will have the pros do the labour....

85.5mm piston kit
84.9mm bigbore sleeves
dual 38 mkuni taper bored carbs

Is this all I need or is there more???:bigeyes: :question:

Thanx in advance!!!

 

[FL-cracker]

Not sure if those carbs will be big anough. Maybe someone esle can answer that.

Also, what head are you running, I think you have to use bigger domes for the big bore, not to sure.

Other then that you will have to bore the cases for the larger sleeves, and I think that is it.

 

[SuperJETT]

The top of the crankcase will need to be clearanced for the sleeves to fit.

 

[Frosty]

Not sure if those carbs will be big anough. Maybe someone esle can answer that.

Also, what head are you running, I think you have to use bigger domes for the big bore, not to sure.

Other then that you will have to bore the cases for the larger sleeves, and I think that is it.

i was thinking the same thing...you might need to go to larger carbs... not sure if 38's will be enough for 85.5mm bore setup.

 

[Idok]

magoo would recommend 44's

 

[Exile]

Thanx for the 44 insight after giving my engine a few ponies at least they should breathe to stay alive! Il def go with 44 then...

What domes are recommended or can I run flattop pistons??

 

[SUPERTUNE]

44mm's should be min...Don't forget the ADA billet girdled head w/somewhere around 38cc domes depending on the porting...

 

[surfgy45]

why go big bore? your going to have all new top end on a probably old crank. then down the line you'll have to rebuild the crank.

Art, over at Jetworks, came up with a great 4mm stroker package. You get a new crank and all the work + a port job i believe at the same price, probably cheaper, than a big bore. With this you'll get the same results with more reliability.

i dont know all the details other than im getting one soon. give Art a call and he'll fill you in and im sure positive you'll like the results!!

 

[Whale]

what size bore can you go up to with out having to re sleave?? im running just standard bore size at the mo and want to go up a size or two??
Any help ??

 

[Exile]

Yamaha stock can bore to 83mm, after that you have to resleeve it, I ve read sum people speculating about boring 84mm stock,too thin I wouldnt do it!!! Go to groupk website and read up on the technicals!!!! Its very helpfull...

 

[Exile]

Thanx sURFGY45 i Think our blokes arent up to the level with cranks as you guys are in the us and australia... If I want the crank and bigger cylinders Il send my engine to the us....

Supertune, I am running Blowsion heads currently on stock bore, what domes might I have in or should I just order the 35cc domes with....and by the way how much are the lamey,magoo cylinders alone???? Ive read so much about them but never a price!!!

 

[waxhead]

groupk in another aticle say they will go to 84.5
so dont read to much into what they say
84 is fine
i have been to 84.25
but well i think its on the limit

 

[unclehulka13]

if you run flat tops, you need flat top domes.
if you run 85mm bore, you need 84mm domes.
dont know if blowsion has em, i know ada does.

 

[SUPERTUNE]

I don't know what Blowsion have for dome sizes?? I use only ADA when I buy heads for my engine builds, I have used other brands but have seen cracked domes with a few of them and have never cracked any ADA domes, even cutting the crap out of them for big strokers!
35cc's will be way too compression for pump gas for a 85mm bore motor, if the porting is right for freeride/freestyle power...

 

[surfjetlouie]

one more to add to the list $$$
Louie

 

[Jr.]

Hi Chuck, Welcome to the X.

I agree with Chuck, Run the ADA head & girdle kit with your build. It will save you on many fronts. I also agree that most rec freeride boats don't need that high of compression

There is a big differance in cyl setup between Yam style domed pistons & kaw style flat tops. The dome style is just a part of it.
the big differance is piston dimensions. The "timing edge" diminsion is 4mm differant. (distance from the top of pin to the top dome edge) the FT is shorter. so the cyl need to be machined accordingly. The skirt will also need to be modified to be used on a std stroke or the skirt will hit the cases.

Many engine builders have differant feelings on the FT/ domed debate.
I personaly like the added power of the FT. But to many the cost of building it is not worth the gain.

as for the carbs, Definately duel 44's, or if your budget permits, 48 Full Specs

Chuck, Please feel free for your comments, as you have already, Your contributions here just took the tech level of the site up a notch. welcome!!

ski ya, Paul