750 big pin seizure !!!!

x2fatkid

x2fatkid

Location
antioch ca
:crazy:Ok here it goes i'm on my 3 seisure in 3 rides.I started this season with a brand new set up..750 big pin motor bored to an 800 cc,46sbn carb, ADA head 155 psi, jetpro exhaust manifold, factory head pipe, blaster limited chamber, westcoast waterbox,notsure of the timing advance but am checking that soon,dual cooling lines all routed right.Blew the motor after 30 min of riding!sent the motor to a freinds shop,he thinks the cylinder is leaking...so he built a new motor put it all back together put it in the water tank did a little carb adjustments raised the pilot to 65 seemed to run better but after checking the plugs looked real lean, also the motor is way to hot.he thinks i have water leak in mycooling system.Pressure checked that all seems good now we think it might be my factory head pipe..he thinks the motor is sucking water back in from the top water screw, it's open 1 turn and the bottom is open an 1/8.Is this even possible? Can it blow from to much adavance on the stator?Forgot to mention i have 650 elec ....I'm almost done with the 750 motors what am i doing wrong
 
Last edited:
SUPERTUNE

SUPERTUNE

Race Gas Rules
Location
Clearwater Fl.
Try setting the headpipe screws closed with only the bottom opened 1 turn for a baseline setting.
To check for cooling problems, pull the waterlines off the tubes inside the engine compartment, hook up a waterhose to them, pull the rideplate, disconnect the waterlines at the feed tubes, now turn on the waterhose and check for waterflow through the tubes, as Kawasaki has problems of the feed tubes collapsing and restricting the incoming water feed.

Next thing to check is make sure your piston to wall clearance is adequate for a hot rod engine, .0045 for cast pistons, .0055 for wiseco's.
Ignition timing check IS mandatory!
You stated a 65 low jet? That can't be right for a 44mm SBN carb.
Should be at least a 120!, depending on the pop-off.
Is this 44 mm carb a stock Yamaha carb? If so get rid of it and buy a SBN 46mm aftermarket!
 
Last edited:
shawn_NJ

shawn_NJ

Chasing waves.
Location
Daytona Beach
Your pilot was 65 on a single 44??? Holy S!!! Thats not good. Basically exact same setup except I run a 46sbn... my big pin is setup 120L 155H 2.3n/s 90g.

Small pins seem to like 150H better.

How advanced is your 650 stator ??
 
Last edited:
x2fatkid

x2fatkid

Location
antioch ca
sorry guys it was late last night when i posted and yes i was wrong my low jet was 120 ,and we changed it to a 125.. my seat and spring is at a 2.0 ..not sure of my high jet all my notes are at my buddies shop.if i can remember right i think my advance is set at 4 degrees.and i think my piston clearance on my last blow up was .0040,is that to tight ?
 
Last edited:
tor*p*do

tor*p*do

Squarenose FTW
Site Supporter
Location
NW NC
um, if it seizes, it was probably too tight (see supertune post)
if you used seize-cos, 004 is not ok
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
With the tight clearance you got on the pistons, you might be over-cooling the engine with dual cooling.
Have you monitored the temperature of the water coming out of the pissers?
 
x2fatkid

x2fatkid

Location
antioch ca
yes, when we put the new moter in the ski and water tested it thats what is concerning us the water seems to hot .and just so we are clear i was told that the pistons where cleared at 40 thousands i think that is .0040 ..sorry worked hard today already had a few beers..
 
Johnny340

Johnny340

Location
Vancouver
4 thou is not that loose for a watercraft engine. Go to 6 thou+ with similar jetting and forget about it. You may loose a couple HP but at least you'll be ridin'.

Sorry to hear your grief! Good luck getting it going. Again.

Have more beer for tonight, though. Tomorrow is another day!
 
x2fatkid

x2fatkid

Location
antioch ca
Well we water tested it again and he thinks it's a timing issue or a bad CDI,he sayed it's detonating in the back cylinder..Either way he said it's not going to leave the shop until it's 100%.
 
shawn_NJ

shawn_NJ

Chasing waves.
Location
Daytona Beach
4 degree advance is aggressive for a bigpin with 180psi. Being that you had a meltdown, put the timing back to stock. What year 650 coil are you running?
 
x2skier

x2skier

Location
Mechanicsburg, PA
I'm almost done with the 750 motors what am i doing wrong
Click to expand...
Now, now, don't be blaming the engine. Post some pics of your pistons. At what point did it fail.....wide open? Same cylinder each time? Are the piston crowns melted? Pitting on the head from foreign debris?
 
X2guy

X2guy

Location
Barrie, ON
I went through all of this when I first built up my 800. Make sure your using a good comp gauge. Not one of the wones with the adapters with about 5cc's of volume in them. What size somes are you running? I have 30cc (the largest for a 750) and I'm getting about 170psi. My port timing has been raised a few mm as well which helps lower compression. however I'm running a small pin cyl so my port timing is probably similar to yours. Without the porting I'd probably be somewhere over 185. Check for pitting around the outside of the piston top. This will tell you if you are detonating.
Next you may very well be seizing due to the clearance you are running. I'm assuming you are running wisecos. Wiseco recomends about .006 for this size piston. I was still seizing with this clearance. I finally set it at .008 and have been fine.
Good luck
 
x2fatkid

x2fatkid

Location
antioch ca
Blew another motor today in the water tank!!!!:crazy:!He called to let me know..I've called wiseco and they recomend 6+ on piston clearence.He just won't here that, he says thats not the problem.He wants me to run aviation fuel atleast 50/50 ,he still believes it's detonating..He says the exhaust is way to hot.
 
You must log in or register to reply here.
Top Bottom