need stroker help

[pontoonkiller]

what i have is a 5mil stroker motor with ported 61x cylinders, 61x cases, coffmans exhaust and dual 44mm blackjack carbs. my problem is that this motor is weak on bottom end but rips from mid to top rpm i am more interested in riding freestyle so i need some low end power. My question would be is this low end power something i can acheive from tuning what i have or do i need to start buying some different parts and info will help

 

[ATS_Aaron]

What prop do you have? and how is that cylinder ported? How is the stroker setup? Does it have relieved domes or a spacer between the case and cylinders?

Aaron

 

[marz831]

Seems a little odd to build a stroker with x cases, no? and a coffman pipe... Not that there's anything wrong, just seems like a unique setup.

 

[ATS_Aaron]

Sounds old. A lot of stroker setups are old. I think they were more common back in the mid 90's before some racing rule change basically outlawed them (or made big bores legal and strokers were deemed expensive?).

I bought a 6mm stroker off Ebay about a month ago. I has 6m6 cases with the reed area cut off and Kawasaki style reed part welded on. Thread on here said it was old school race mod from back in the days before the 62T existed.

Aaron

 

[Foximus]

Sounds old. A lot of stroker setups are old. I think they were more common back in the mid 90's before some racing rule change basically outlawed them (or made big bores legal and strokers were deemed expensive?).

I bought a 6mm stroker off Ebay about a month ago. I has 6m6 cases with the reed area cut off and Kawasaki style reed part welded on. Thread on here said it was old school race mod from back in the days before the 62T existed.

Aaron

lol you bought that?


I was watchin that and wondered who the sap was that bought that.

Does it run good?

 

[pontoonkiller]

it does not have the spacer plate it has a milled head i will have to recheck my impeller for numbers but i do know it is a solas that is recommended for a stock 701 superjet. the setup was givin to me from the dealership i used too work at and it was told to me that it was an old race motor. i also have an old 6m6 engine that came out of this boat that has 61x cylinders on it. i don't know the port timing

 

[#ZERO]

No spacer plate and a stock milled head? :scratchchin:

Did you ever remove the cylinder head to look inside the engine?

 

[Shonuff]

No spacer plate and a stock milled head? :scratchchin:

Did you ever remove the cylinder head to look inside the engine?

Don't leave us hanging . . . what's he looking for?

 

[Mouthfulloflake]

one hell of a dome cut on a stock head I would assume.

 

[pontoonkiller]

the head is not stock it says triton eng. on the top. ive never heard of them before. i did look in the engine and the cylinders are ported but longer and i read where that is for high end. the impeller i am running is a solas yb-sc-i 14.5-18. Should i try a different port job, exhaust, carbs or what. what i don't want to do is get rid of parts that will help make my lowend power but i do need to change something. just don't know where to start

 

[tom21]

yeah the stroker I just picked up has a mrd head that has the domes cut deeper in the head for the extra throw.

 

[#ZERO]

When the head was off did you happen to notice that the pistons where higher then the cylinders deck surface? Also the domes squish band should have but cut deeper to compensate for the extra piston height.

You will find that the Yamaha 701 61x has a below-deck exhaust port height of 39.6mm, with a width of 48mm. All the transfers are the same height - 55.4mm. The main transfer port width is 31.75mm, the auxiliary transfer is 25.4mm wide, and the boost port is 21mm wide. If it's a stroker cylinder they should have lowered the port window a few millimeters. You may want to install a degree wheel and check the port timing, duration and blowdown time.

Also check your jetting and post what size needle & seat, pilot, main, spring you have.