Super Jet Mild Pistons scoring and seize HELP

[Andersschroder]

I was going wot for like 45 sec and when i let off the gas the engine died briefly. It took a couple of tries to start it up again. I took off the head followingly and noticed som mild scoring on the cylinder wall. This has happened a few times and worries me.

I have perfect piston wash and spark plugs colors. And it pulls and idles perfectly. It has Identical perfect compression.

I have a restrictor before the pisser tuned for 50-60 C (120-140 F) measured on the the surface of the cylinder. But the seizure has happened in cold water with and without restrictor.

Sea Water temp is 6 C (42 F).

I used a high quality oil.

Msd enhancer, bpipe, open air filters, stock head and everything else is stock. 135 hi, 70 lo, 1.5 NS, 95 g springs.

What the heck is wrong?



Sent from my iPad using Tapatalk

 

[zzylstra]

Is it snagging rings on the ports?


Sent from my iPhone using Tapatalk

 

[augustaf]

If the plug colors look good as stated, you may still need to open the top needle adjustment(s) about 1/8 turn, it might have been too lean on top. Also, have you ever checked your squish? One millimeter is just not enough, 1.2 -1.3 would be better. If you are using an ADA head, you might notice that the domes are only recessed 0.015" (about 0.32mm) . Compare that to the stock 1mm thick headgasket. I've had a bit of a problem with that a few times- put the domes in a lathe and increased squish depth, rather than removing cylinder and installing a thicker base gasket.

 

[JetManiac]

If the plug colors look good as stated, you may still need to open the top needle adjustment(s) about 1/8 turn, it might have been too lean on top. Also, have you ever checked your squish? One millimeter is just not enough, 1.2 -1.3 would be better. If you are using an ADA head, you might notice that the domes are only recessed 0.015" (about 0.32mm) . Compare that to the stock 1mm thick headgasket. I've had a bit of a problem with that a few times- put the domes in a lathe and increased squish depth, rather than removing cylinder and installing a thicker base gasket.

He has a stock head.

 

[Andersschroder]

Sent from my iPad using Tapatalk

 

[Andersschroder]

Is it snagging rings on the ports?


Sent from my iPhone using Tapatalk

Oy zzylstra, yes it looks like the scoring is around the ports. Check the pics. Whats the verdict gentlemen?



Sent from my iPad using Tapatalk

 

[Nuklear6]

How long has the engine been together with those pistons? Has it been over bored?

My observation is the piston wash is a little dense/thick for a short time of running (again don't know how long the engine has been together). That would be a tell tail that (as said above) you could be a hair lean on the top end.

If it has been over bored and pistons changed I would immediately have the piston to cylinder wall clearance checked with a real sunnen style bore gauge (NOT with calipers or feeler gauges). Also while apart to measure the bore clearance make sure to measure the ring end gaps on every ring. Too tight on either the piston clearance or the ring end gap could give you similar problems to what you're having

Thanks

Chuck Palmucci
CPT Enterprise LLC
609 510 3062

 

[Andersschroder]

How long has the engine been together with those pistons? Has it been over bored?

My observation is the piston wash is a little dense/thick for a short time of running (again don't know how long the engine has been together). That would be a tell tail that (as said above) you could be a hair lean on the top end.

If it has been over bored and pistons changed I would immediately have the piston to cylinder wall clearance checked with a real sunnen style bore gauge (NOT with calipers or ************ gauges). Also while apart to measure the bore clearance make sure to measure the ring end gaps on every ring. Too tight on either the piston clearance or the ring end gap could give you similar problems to what you're having

Thanks

Chuck Palmucci
CPT Enterprise LLC
609 510 3062

Its a 2009 engine, never done a thing to it.
The thing is that i have tried to give it 1/4 turn out on the hi jet and it just made hole shots a bit lagging and not as snappy as it is now.

 

[zzylstra]

You have a pretty good chamfer on those ports I don't think it's catching a ring


Sent from my iPhone using Tapatalk

 

[augustaf]

Sustained wot operation in 6 deg. C water (that's cold!), can be a problem. Cylinder walls might be cold, high rpm-lots of power- almost instantly raises the piston temperature. Compared to the cylinder sleeve, the aluminum piston has twice the coefficient of expansion. There goes your 0.1mm piston to wall clearance! Running to lean at high rpm also heats the piston top a lot. I've certainly ridden in freezing water myself, hand warmers and all- but I suppose the wind chill in my face kept me from going very fast.

 

[Andersschroder]

Sustained wot operation in 6 deg. C water (that's cold!), can be a problem. Cylinder walls might be cold, high rpm-lots of power- almost instantly raises the piston temperature. Compared to the cylinder sleeve, the aluminum piston has twice the coefficient of expansion. There goes your 0.1mm piston to wall clearance! Running to lean at high rpm also heats the piston top a lot. I've certainly ridden in freezing water myself, hand warmers and all- but I suppose the wind chill in my face kept me from going very fast.

But am i running lean?!


Sent from my iPhone using Tapatalk

 

[Jr.]

When I set up a motor to your spec, I Jet as following:
137.5 mains, 75 pilots, stock needl/seat & springs
Adjusters 1 & 1 , then tune from there
That is for pump gas here in the US.
Your fuel is different I'm sure?
That said, and judging by your specs in first post?
I would say you are fuel lean?
The pics of your piston crowns is showing residue from your oil, not fuel burn.

 

[Andersschroder]

When I set up a motor to your spec, I Jet as following:
137.5 mains, 75 pilots, stock needl/seat & springs
Adjusters 1 & 1 , then tune from there
That is for pump gas here in the US.
Your fuel is different I'm sure?
That said, and judging by your specs in first post?
I would say you are fuel lean?
The pics of your piston crowns is showing residue from your oil, not fuel burn.

I run 95 octane here in Denmark. But i dont get it? These were the jets specified by the bpipe manual for this setup.

Also if i give it a bit more hi-jet like 1/4 turn out, it looses the snappyness during holeshots. What am i doing wrong?


Sent from my iPhone using Tapatalk

 

[Jr.]

That is controlled thru the pop off. I suggest you put the stock spring back in (115 gr)
Also, FPP jetting is just a starting point. I have found it is lean overall.

I have little experience comparing fuel us vs euro ratings? I can't make comment to that

 

[Andersschroder]

So you think its a lean issue rather than a cold issue based on the images? How should they look then cause i thought they looked perfect?

Also what popoff pressure should i look for?



Sent from my iPhone using Tapatalk

 

[Jr.]

Thus far I have not made comment to cause of seizure? Simply because not enough information is known? Or what severity of damage the first event caused?
The seizure does exhibit that of a 4 point seizure, so I Could assume water temp has played a part in this? I'm guessing this is caused my multiple issues?

Pop off should be approx 55#

 

[Andersschroder]

Thus far I have not made comment to cause of seizure? Simply because not enough information is known? Or what severity of damage the first event caused?
The seizure does exhibit that of a 4 point seizure, so I Could assume water temp has played a part in this? I'm guessing this is caused my multiple issues?

Pop off should be approx 55#

Thank you so much. Yeah my original post was about why it seizes after decceleration from wot. In cold water. But as stated in my first post i have tried to restrict the cooling for it to not overcool. All that happened was a brief seizure and then the scoring in the images happened. If i can provide anymore info for you to pinpoint the problem ill be happy to. Most of the info i have was in my first post.




Sent from my iPhone using Tapatalk

 

[Big Kahuna]

When you went from WOT to nothing did you just straight cut throttle or did you feather it any to keep some fuel flowing?

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[Andersschroder]

I honestly cant remember. I just feels like running out of gas. Then a couple of hard starts and i fires back up.


Sent from my iPhone using Tapatalk

 

[Big Kahuna]

I have stuck pistons running out of gas on a single carb setup before a few times. Also from being on the edge of lean and running WOT and chopping the throttle. Pistons are really hot at this point then you cut off any fuel and it can stick. But listen to Jr.