swapping from a 701 to a 650

[Mouthfulloflake]

so I pulled the 701 out of my black boat today to pressure test.

It was running strange, hard to start in the water ( easy on the trailer), acted flooded all the time.

swapped carbs, fixed needle and seat. still not running right.

so pressure test, it held, had some SMALL leaks around my carb and exuast block off plates, when I neared 15 psi.

I think the engine is just worn out, even with an aftermarket head its only showing 150 psi.

anyway, swapped in a 650 in its place, with a lightened flywheel, stator advanced, and an MSD enhancer, mariner head, and coffman pipe.

we will see how it compares.

I guess that 61x 701 will come apart this winter, and get a bore ad pistons, and some port openeing love.

 

[S&Ssuperjets]

Get some rings and finish out the season:crutches:

 

[Mouthfulloflake]

Get some rings and finish out the season:crutches:

well, finishing the season was my goal with swapping in an engine that I KNOW runs.

if I tear into the 701, even just for rings, im out... how much? $40 for rings? $40 for gaskets?

thats halfway towards finishing the 735 freestyle ported engine that ive been working on.

actually, im not sure the low compression is whats making the 701 run poorly.
im just tired of it sitting on the beach, and consuming my time, I just want to make it rideable for now.

swapping engines is just a step in the troubleshooting I guess.

ive been thru the carb and ignition.

 

[S&Ssuperjets]

tired of it sitting on the beach, and consuming my time .. I feel your pain :banghead:

 

[Mouthfulloflake]

tired of it sitting on the beach, and consuming my time .. I feel your pain :banghead:

my beach isnt even that nice.

:banghead:

 

[S&Ssuperjets]

Thats the lake jetski cove

 

[Freestyleriverrat]

Yeah, the compression is not your major issue, it sounds like a carb problem. Did the motor run ok with those carbs previously? How were the reeds? My ski started running like crap one day and I thought I bent an rod. Tore the motor down and the culpret turned out to be a cone from my prok flame arrestor came off and choked 1 carb.

 

[Mouthfulloflake]

thats part of the rub, I bought the engine used ( a few years ago) and never ran it until this spring.

so I odnt know if it EVER ran right, reeds are stockers, that I put in, they looked ok.

compression was 120 ish before the westcoast head. now its 150 ish.

if you could ever feather the throttle enough to get it running in the water ( pure lucky) then it would pull hard on mid to top end.
it NEVER had a sharp bottom end thoough.

upon recommendation from magoo FU, its running the same jetting as a B pipe ( or very similar) but instead running a coffman sizzler ( a 650 pipe) with the manifold opened up to match the 701 engine.

61x from a 1994 blaster.

swapped carbs completely, before I replaced the needle and seat, same issue.

could it be just jetted TOO fat?

the exhuast was HOT as hell when it was running though, it melted the negative battery cable.

any ideas and nput are appreciated!

Yeah, the compression is not your major issue, it sounds like a carb problem. Did the motor run ok with those carbs previously? How were the reeds? My ski started running like crap one day and I thought I bent an rod. Tore the motor down and the culpret turned out to be a cone from my prok flame arrestor came off and choked 1 carb.

 

[Moondance]

Yeah, the compression is not your major issue, it sounds like a carb problem. Did the motor run ok with those carbs previously? How were the reeds? My ski started running like crap one day and I thought I bent an rod. Tore the motor down and the culpret turned out to be a cone from my prok flame arrestor came off and choked 1 carb.

you too? had a buddy just rebuild his flat top; he was making a couple of passes & wham...he's over the bars. I literally saw dollar signs spin in his eyes & the oh sht look. Pulled the hood & saw it immediately. Easy fix & color quickly returned to his face:biggrin:

sorry.....hijack over

 

[Mouthfulloflake]

ive tried 2 different air filters stock, and an old KnN.

same problem.

im at a loss.

keep the ideas coming though.
thinking is good for my hangover.

 

[Moondance]

ive tried 2 different air filters stock, and an old KnN.

same problem.

im at a loss.

keep the ideas coming though.
thinking is good for my hangover.

beer is good for your hangover:sneaky:

 

[Mouthfulloflake]

I work in a very laid back environment, but beer in the office this early would get me in trouble.

:biggrin:

lunchtime though, thats a whole other story.

 

[douglee25]

I think the problem is right under your nose (maybe?). You said with the stock head you were around 120psi? That is really low for even a stock head. If the compression was that low before the head install, I would bet that a complete rebuild is in order.

Doug

 

[Mouthfulloflake]

I think the problem is right under your nose (maybe?). You said with the stock head you were around 120psi? That is really low for even a stock head. If the compression was that low before the head install, I would bet that a complete rebuild is in order.

Doug

possibly, but ive engines with low compression before that ran better than this.

they were tuned well initially though, this one wont really run well enough to get dialed in.

it could be a combination of the two things.

 

[douglee25]

possibly, but ive engines with low compression before that ran better than this.

they were tuned well initially though, this one wont really run well enough to get dialed in.

it could be a combination of the two things.

It sounds like low compression combined with an air leak to me. I don't doubt your mechanical ability and therefore it makes me think that you're chasing your tail with some sort of air leak. Have you pressure tested it yet?

Doug

 

[Mouthfulloflake]

It sounds like low compression combined with an air leak to me. I don't doubt your mechanical ability and therefore it makes me think that you're chasing your tail with some sort of air leak. Have you pressure tested it yet?

Doug

I pressurised it last night, my block plates for the carb and exhuast where whistleing a bit as I got to 15 psi.

I heard and saw no other air coming out.

 

[douglee25]

I pressurised it last night, my block plates for the carb and exhuast where whistleing a bit as I got to 15 psi.

I heard and saw no other air coming out.

And the plot thickens.... If the motor is tight, you are correct that it should still run on low compression. I would lean towards what others have suggested in the carb tuning.

Doug

 

[2002zxi]

hey instead of watching the hogs get demolished this weekend, lets just have a superjet wrenching party!

 

[Mouthfulloflake]

haha!

IM not sure what our plans are yet, I think I have to work late Friday night though, that sucks.

2 different freinds having keg/watch parties at their houses.

wife wants to goto the lake.

Id rather sleep at this point.