750 big pin seizure !!!!

[x2fatkid]

: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

[tom21]

well if the plugs look lean, you think you might try rejetting so its not lean?

[SUPERTUNE]

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!

[madscientist]

the jetting seems way off. listen to supertune!!!!!!!!!!!

what is your main jet? it should be around 140-150 min for that motor.

[shawn_NJ]

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 ??

[x2fatkid]

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 ?

[tor*p*do]

um, if it seizes, it was probably too tight (see supertune post)
if you used seize-cos, 004 is not ok

[Matt_E]

What water temperatures are you running in?
Dual cooling?

[x2fatkid]

califonia delta maybe 68!! and yes duel cooling lines.

[Matt_E]

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]

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]

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]

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]

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]

I'm almost done with the 750 motors what am i doing wrong 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?

[orangefinger]

delta water = very dirty water ...check cooling lines you might have sucked something up....

[X2guy]

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

[Scorn800]

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%.


Make sure the boat is not over proped.

[x2fatkid]

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.

[tor*p*do]

I've called wiseco and they recomend 6+ on piston clearence.He just won't here that, he says thats not the problem.

they don't call them seize-co's for nothing!

[SUPERTUNE]

they don't call them seize-co's for nothing!

That's not fair! Just somebody using a over aggressive squish and chamber design can cause detonation even at lower compression ratio's. Wiseco pistons don't like a lot of piston crown heat...You should look at the headpipe size and make sure it's not too small as this will cause these problems.

[madscientist]

hey chuck, i am setting up my 750 now and i could use some jetting help.

SMALL PIN 750 :
1. EXHAUST PORTS CLEANED UP not a lot of material removed, and polished
2. TWIN 40 MM KEIHIN FROM AN XIR
3. BLASTER FPP LIMITED CHAMBER
4. MSD T/L SINGLE CH. ANALOG
5. WESTCOAST HEAD W/ 29 CC DOMES ( 190PSI)

HAVE 68 LOWS AND 130 HIGHS NOW AND LOOKING TO ORDER NEW JETS AS DIRECTED

[SUPERTUNE]

Maybe with 44 or 46 Mikuni's...I never thought in a million years that I should have kept more jetting notes for the past 30 years!, with the last 20 with PWC (jetski's).
Duh! Never thought that I wouldn't remember...

[tor*p*do]

That's not fair!.

maybe not,
but if not set up just right (and I do not doubt that you know how)
they are not very forgiving and
you can have problems

[x2fatkid]

What about water leaks in the casting ,of an almost brand new jetsport exhaust manifold.With only 3 rides....blew the motor each ride.Thats what the latest news is on my motor.tested under water all sealed up and filled with air..would that continue to blow the motor every ride?

[X2guy]

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.

He better start hearing that or he's going to keep scuffing your pistons. That's just the way wisecos are. you cant run OEM clearances. I've been there. Post pics of the pistons.

[X2guy]

What about water leaks in the casting ,of an almost brand new jetsport exhaust manifold.With only 3 rides....blew the motor each ride.Thats what the latest news is on my motor.tested under water all sealed up and filled with air..would that continue to blow the motor every ride?

Yes. First if the exhaust manifold leaked it would only blow the water into the pipe. If it was running low piston clearance it would seize even if the engine didnt leak air. Wisecos suck if you ask me. Run Pro X. I run 83mm wisecos in my small pin as there are no others and I run .008" clearance.

[x2fatkid]

750 big pin motor bored to an 800 cc,44 carb, ADA head 180 psi, modified stock 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 . Any advice on where my jetting should be? Right now needle and seat is a 2.0 low is at 125 not sure of the high jet..my guy water tested my ski on tue and he said that thejetting was close on the bottom but way to lean on top . and he thinks he will have to hone and put in new rings before he rejets. Anyone running a similar setup? looking for some jetting advice...Thanks:beerchug:

[2XLR8]

I would start with at least a 155 main and I would make sure I did not have the 115 gram spring and maybe not even the 95 gram spring. I don't understand why you have to hone and replace the rings again?

[X2guy]

Can you post pictures of the pistons? Is it a lean seize or a cold seize. Cold seizures usually have the 4 corners of the pistons scuffed.

[x2fatkid]

Sorry but i live about 60 minutes from my buddies shop and i have not seen the pistons.From what he has told me it sounds like it is a 4 corner seizure.I don't think that there has been any real piston damage,mostly cylinder scuffing.Again i have not seen any of the 3 sets of pistons that have come out of my ski yet.my ski has been in sac since 3 weeks before memorial day,hoping to have it back before 4th of july:dunno:

[shawn_NJ]

I hope this guy isnt charging you anything.... Get a mechanic who will set the motor up to with the clearances Wiseco told you. Nuking a motor 3 times is rediculious.

Until you get a handle on the problem. You should be 100% sure you are not running ANY timing advance. My big pin motor with 205 compression did deto with the 650 stator 5deg advanced, and 93 oct. You could hear it "pinging". Solved with running 50/50 race gas/93 and backing advance down to 3deg. I personally would also throw a stock head on the motor. And start with a 160main and work back.

[X2guy]

Sorry but i live about 60 minutes from my buddies shop and i have not seen the pistons.From what he has told me it sounds like it is a 4 corner seizure.I don't think that there has been any real piston damage,mostly cylinder scuffing.Again i have not seen any of the 3 sets of pistons that have come out of my ski yet.my ski has been in sac since 3 weeks before memorial day,hoping to have it back before 4th of july:dunno:

Tell him to use at least .006" clearance. I set mine up with 8 as I had so much trouble. Now that I bore my own cylinders I have found it very suprising when setting up a cylinder using oem pistons. I have a hard time using only .0025" in some cases. Has he had not much experience with wisecos?

[kevbo]

You can stick an OEM piston just as fast as a Wiseco if the setup is not correct.

[x2fatkid]

He is not using weiscos this time i believe they are WSM,and he said that he set them up at 5 thousands .I think he should have it dialed this week,all he has to do is put new rings and hone it again,he thinks that there was some light scuffing due to the lean carb..sounds like 160 is a good starting point.Thanks for checking my post,i just wish i could give you all better feedback and picks for you're trouble.

[x2fatkid]

Ok got the ski back still need jetting advice..how about 120 low 180 high jet, 2.0 needle and seat? 1 1/4 out top and bottom screw..I tried 110 low 215 high 2.0 needle and seat bogging real hard when i turn right and left!! plugs look good though,any help would be nice.. I know 215 seams really big but the plugs looked lean last night in the dark!! O -yeah pistons are clearanced at 7 thousands

[BlueBreadTruck]

ive had great luck with wisecos...I have 2 seasons on my 800 and still has 180 psi.

Now, what head are you running? For me, with the 800 cc bore, i use the stock head to get 180 psi....about the max i would want to run. I hold mine WOT for long periods with no issues, but im also running 750 electronics with NO advance

[shawn_NJ]

Ok got the ski back still need jetting advice..how about 120 low 180 high jet, 2.0 needle and seat? 1 1/4 out top and bottom screw..I tried 110 low 215 high 2.0 needle and seat bogging real hard when i turn right and left!! plugs look good though,any help would be nice.. I know 215 seams really big but the plugs looked lean last night in the dark!! O -yeah pistons are clearanced at 7 thousands

If you want 46SBN specs....I have (3) 750 X2's, all piped with 46sbns. Been running for 2 years with this jetting. Also know a bunch of other 750 x2s running these specs.

120L
150H
2.3n/s 95g
Stock SuperJet FA

[x2fatkid]

If you want 46SBN specs....I have (3) 750 X2's, all piped with 46sbns. Been running for 2 years with this jetting. Also know a bunch of other 750 x2s running these specs.

120L
150H
2.3n/s 95g
Stock SuperJet FA
Are you running a blaster limited chamber on any of them?Also my head pipe says mariner/factory pipe..it only has 2 water screws,any advice on where they should be set at?I think i will try a 46sbn on my ski this week with those settings.Thanks ..what are you're high low srews set at?

[shawn_NJ]

Are you running a blaster limited chamber on any of them?Also my head pipe says mariner/factory pipe..it only has 2 water screws,any advice on where they should be set at?I think i will try a 46sbn on my ski this week with those settings.Thanks ..what are you're high low srews set at?

I am running the SJ mod chamber on one and a coffman on the other. Jetted the same within a 1/6th of a turn. You have a very very old headpipe made for 650's. I had one of those years back, it needed to be bored out to atleast 47mm!! If its the stock 40 or 42mm opening this is not sufficient for your setup, and could be one possible reason you are burning pistons. (As Chucky mentioned in post #21) What is the diameter of the opening in the headpipe and ex manifold?

[shawn_NJ]

Does it look like this one? ie no bottom screw.

http://www.surf-mb.com/750/2screw.JPG

[x2fatkid]

Yes it looks just like that! I'm not sure the diameter,i'll have to check it next time i have it off.I'm going to take the ski to a shop today that jetted my ski last year with great success,we will see if they can make this set up work just as well.I have not worked since dec so money is tight but they are pretty sure they can get it right in about an hours labor..If that is the case then it is well worth the 106.00 per hr.I just want to ride my ski ..already had a taste of the power again compared to a 650,i know why i wanted a 750/800 motor.

[shawn_NJ]

Pull that headpipe/ex manifold and check the diameter before you run it! That oldschool 650 headpipe is a POS, trust me I had one. If its too small odds are your just going to cook another topend. Save the $$$ you are going to give hte shop and get yourself a 46sbn. Jet it as I posted and you'll be really happy. If the shop isnt actually going to ride it the tuning will be subpar anyway.


Where is your 650 timing set to?

[x2fatkid]

Ok just put a 46 sbn with you're jetting specks 2.3 n/s 120L 150H on will water test maybe Thu/fri .What should i set the fuel screws at?Do you think some of the piston problems are related to the blaster chamber?And the head pipe and manifold have been opened up not sure of the diameter..

[shawn_NJ]

Ok just put a 46 sbn with you're jetting specks 2.3 n/s 120L 150H on will water test maybe Thu/fri .What should i set the fuel screws at?Do you think some of the piston problems are related to the blaster chamber?And the head pipe and manifold have been opened up not sure of the diameter..

Cool! Bunch of guys are running the blaster chamber so that shouldnt be an issue. Do you know where your 650 timing is? You are still going to have to tune the screws. You can tune the low speed on a submerged trailer with the ski strapped down. Groupk has a great write up for this and its not hard to get that close to dialed in. For the high speed, turn it 2 out and check the plugs after a 15-20sec WOT chop. Do what the plugs tell you if you dont have a tach. I believe my coffman pipe ski is 3/4 out on the high, and my FP SJ chamber ski is 1Turn out, or something right around there.

[x2fatkid]

Cool! Bunch of guys are running the blaster chamber so that shouldnt be an issue. Do you know where your 650 timing is? You are still going to have to tune the screws. You can tune the low speed on a submerged trailer with the ski strapped down. Groupk has a great write up for this and its not hard to get that close to dialed in. For the high speed, turn it 2 out and check the plugs after a 15-20sec WOT chop. Do what the plugs tell you if you dont have a tach. I believe my coffman pipe ski is 3/4 out on the high, and my FP SJ chamber ski is 1Turn out, or something right around there. Not sure of the timing but was told it is very minimal.Thanks for you're help i'll try those settings my self..

[x2fatkid]

Do you have to bore the head pipe and the manifold?The manifold is a stock TS mani opened up not sure of the size...Ran the ski twice now once with a2.3n/s 120L 150H with the blaster chamber,ran pretty crappy i think it was to rich on the bottom,might of fouled the pluggs.messed with the screws a bunch but i think my pluggs were shot.So i decided to change a few things,pulled the intake mani and reeds.resealed and replaced the reeds,not sure anything was wrong with the reeds but the petals don't seal on the reed blocks.Had another set of FMF torq reeds so i just changed them..also decided to go back to the 650 chamber,and a new set of pluggs just to see if that would help. Ran the ski again Sat not much better ,still boggs on the bottom..closed the bottom screw to 1/2 turn seemed to get better!So i put a 110 L and a 155Hput it back together gave it another try..little betterstill not right..also opened my water screws up the pipe, was very hot sizzeled all down the chamber and tailcone.2 turns on top and bottom,still hot!The ski runs great from mid to full throttle boggs on the low .I think that my gas tank is not pressurizing,would that have an affect on the low end only?And i am going back to the blaster chamber, hits harder and it seems to run cooler..still rode all day just not much lowend.I think i will try a different fuel pickup and seal, if i can find one.I think i'am close just not that great at carb tuning!

[x2fatkid]

bump

[WB1994]

The tank does not preasureize.

[shawn_NJ]

So i decided to change a few things,pulled the intake mani and reeds.resealed and replaced the reeds,not sure anything was wrong with the reeds but the petals don't seal on the reed blocks.Had another set of FMF torq reeds so i just changed them..!

When your troubleshooting you should not go "change a few things". Just going to make it much harder to isolate the problem. I'm confused...Are you saying that before (or now) the reeds are not sealing against the blocks? That will make it run like complete ass (if at all). Start there. Make 100% sure the reeds ARE sealing PERFECTLY against the blocks. I would also recommend putting the jetting back to where I told you and retry.

BIG PIN motors do not have great bottomend, but it still should run pretty good if setup correctly. Looks at this reed picture, this tiny problem caused my skis to run with HORRIBLE lowend. Messed with the carb for a few weeks before I broke down and checked the reeds. Swapped them with another set of stockers and instantly fixed.

http://www.surf-mb.com/7502/rear2.JPG

[x2fatkid]

When your troubleshooting you should not go "change a few things". Just going to make it much harder to isolate the problem. I'm confused...Are you saying that before (or now) the reeds are not sealing against the blocks? That will make it run like complete ass (if at all). Start there. Make 100% sure the reeds ARE sealing PERFECTLY against the blocks. I would also recommend putting the jetting back to where I told you and retry.

BIG PIN motors do not have great bottomend, but it still should run pretty good if setup correctly. Looks at this reed picture, this tiny problem caused my skis to run with HORRIBLE lowend. Messed with the carb for a few weeks before I broke down and checked the reeds. Swapped them with another set of stockers and instantly fixed.

http://www.surf-mb.com/7502/rear2.JPG
Yes the reeds that i had in there before did not seal so i replaced them.most of the petals looked like the bad one in you're pic..I did run the ski with you're jetting after i changed the reeds and it still was not right,it ran alittle better with the bottom screw almost all the way in ,so i lowered the pilot jet and it helped a little,i also went up on the main.It's loading up on the lowend.i'm checking my tank and pickup today or wed.

[x2fatkid]

Well i took the ski to the ski clinic in antioch for performance tuning.But before i did that i had the head pipe and manifold match bored to 47mm.Took it out last sat ran alittle better but not much...they replaced the butterfly and throttle assembly,because the week before a e-clip fell off and messed it up.They set the jetting at 155H 120L 2.3 95gram spring 1turn out top and bottom screw.The ski still boggs and falls on it's face when i turn hard right,and when i take off from shore it takes atleast 3-5 seconds to clearout and get up to plane! So on monday i took it back to them and they water tested it again,the owner derrick actualy rode the ski for about 15min and confirmed that the jetting was fine but it still falls on it's face when you turn hard right,and it stil loads up when taking off from shore.He thinks that there is to buch water in the exhaust,suggested that i try closing the bottom screw and opening the top screw only a half turn.Tryed that yesterday and that did not help much.Going to try and open the bottom a half turn and close thetop screw se if that helps ...keep in mind that i have an old head pipe that only has 2 screws,top and middle but i call it the bottom screw.the next test would be to swap the head pipe for a freinds head pipe thats newer but still only has 2 screws.If that works then i will check my head pipe for internal leaks.Will the pipe run too hot with all th screws closed?

[shawn_NJ]

Is the carb holding 20ish psi on the popoff? Have you eliminated all extra fuel system BS (bypass on/off/res switch). 1 line strait from RES fitting on the tank to the carb IN, and 1 from the return on the carb back to the tank? I had a leaking primer that was letting air into the system. It would make it almost impossible to start if you fell off and it would stumble getting going.

[madscientist]

if the primer line is run to the old oil inj, fitting it will draw extra fuel in at different rpms through the primer. also run the primer on the return line side of the fuel lines so by pumping it you are also priming the carb internals. . the ouput side of the primer needs to be above the butterfly to eliminate the carb vacume from drawing from it.

this could be your culprit

[x2fatkid]

Not sure of the popoff ,but i have lost all the extra fuel selector bull :-):-):-):-).Jetting is set at 155H 120L 2.3 95 gram spring,should be about 20psi..On another note how much air do you need coming in to the engine compartment? My air intake has been filled and i have a 2" opening in the back of the hood hump..
DSC00071

[x2fatkid]

[QUOTE=x2fatkid;784740]Not sure of the popoff ,but i have lost all the extra fuel selector bull :-):-):-):-).Jetting is set at 155H 120L 2.3 95 gram spring,should be about 20psi..On another note how much air do you need coming in to the engine compartment? My air intake has been filled and i have a 2" opening in the back of the hood hump..
DSC00071
[/QUOTE My KTM 450 runs way better than my X2! Well its that time again,the motor is back up and running after i blew it up again...New pistons rings and back down to a 750 small pin cylinder,still not right i'm going to pull the cylinder off and have the clearances checked! he says he put it at 40 -45 thousands. I think that is to tight..What do you think?