SXR Please identify this flywheel -SXR 800

[IceRocket1286]

I am helping someone with an SXR and I do not recognize this flywheel. He has burned a hole in the front piston right under the plug likely due to detonation, probably too low of octane, maybe too much timing advance. Tearing it down for a rebuild. Unfortunately this ski is new to him and this was tank #2 of fuel.

Humor me, can a lightweight flywheel contribute to an increased risk of detonation? I’d say no, but I’m curious as to what others think. Maybe this is far fetched, but are some aftermarket flywheels advanced from their manufacturer? It’s just a thought that popped into my head when I didn’t recognize this flywheel. The magnets would still be 180 degrees apart, but maybe their position on the flywheel is already advanced.

I won’t be able to get my eyes on this motor until the weekend, I plan on seeing if the CDI is stock or aftermarket as well.

Ski info:
2004 SXR 800
Factory Wet pipe - dual cooling
ADA Racing head - 28cc domes - 165/165 PSI when purchased a few weeks ago
V force 3 Reeds and spacers
OEM carbs jetted with tornado filters
RD pump stuffer cone
Motor has been rebuilt before, it has a Hot Rods crank, yuck!
Leak down test : motor held pressure, no air leaks.

All other parts assumed to be stock at this time.

He ran 91 or 93 octane, I forget which. This ski is just like identically built skis in our group, except they have 30cc domes and an OEM flywheel. They also are running around 175psi and no detonation issues. Obviously gasket height and other things play a factor in this, we are just getting started trying to sort it out and get all the details.

Thanks for any information provided!

 

[Big Kahuna]

Wilderness? Rad or Jettinetics

 

[IceRocket1286]

Wilderness? Rad or Jettinetics

It doesn’t seem to have the same hole pattern as RAD and definitely not the current Jetinetics, unless they’ve changed over the years. The Rad holes are circles and these seem oblong. Maybe @MTRHEAD recognizes it. He seems to have an eye for all the parts I don’t recognize haha.

 

[Big Kahuna]

Damn autocorrect.

Vilder.

 

[fastgtfairlane]

It almost looks like thr front cylinder went lean. The rear piston piston wash looks good.. Typically the rear cylinder goes first in that type situation due to heavier load being closer to the pump. I'd also check the crank while you have it apart. Did you happen to do a leakdown before teardown?

 

[mikesx]

Without a doubt an old Jetnetics

 

[WFO Speedracer]

I was also going to say Jetinetics , the older style was all aluminum , the newer style had a steel insert at the flywheel taper.

 

[Storbeck]

Does it have one of those ignition advancer things that move the pickup to add advance? I think some of the aftermarket flywheels had advance built in so if that was combined with the little advancer bracket you might have super advanced ignition.

 

[Storbeck]

And now I read your original post and realized that's exactly what your we're asking, oops. Seems like a possibility but it wouldn't be the magnets, it's the lumps on the outer perimeter of the flywheel that trigger the ignition, magnets don't matter at all you could remove them and an sxr will run as a total loss ignition. St the flywheel next to a stock one line up the keyways and compare the locations of the lumps.

 

[IceRocket1286]

Without a doubt an old Jetnetics

View attachment 450991View attachment 450993

I'm not sure it is this flywheel, the holes are not round like the jetinetics and there are 8 phillips head screws on the engine side of the flywheel as opposed to 4 on the jetinetics you posted. It could be an older, different jetinetics...I'll know more when I get my eyes on it friday. Trying to to some homework before I get back home to work on it. I do plan on doing a side by side comparison with an oem flywheel.

 

[IceRocket1286]

It almost looks like thr front cylinder went lean. The rear piston piston wash looks good.. Typically the rear cylinder goes first in that type situation due to heavier load being closer to the pump. I'd also check the crank while you have it apart. Did you happen to do a leakdown before teardown?

Yes and the engine held pressure. I'm going to check the carbs thoroughly, haven't yet ruled out a lean condition.

 

[IceRocket1286]

It almost looks like thr front cylinder went lean. The rear piston piston wash looks good.. Typically the rear cylinder goes first in that type situation due to heavier load being closer to the pump. I'd also check the crank while you have it apart. Did you happen to do a leakdown before teardown?

Agreed, I would think detonation would cause both cylinders to have similar issues. I'm pretty sure this was a basket case/thrown together ski so I'm not ruling anything out. The unfortunate part is the owner let a friends kid ride the ski and we have no idea what symptoms it was giving or how it was being ridden....presumably wide open. When he first picked up the ski he putted around and checked for the usual, did a few wide open pulls to test it out and was in the process of getting familiar with a new-to-him ski. The owner probably ran 1-2 gallons through it in total. Oh well.

 

[mikesx]

I'm not sure it is this flywheel, the holes are not round like the jetinetics and there are 8 phillips head screws on the engine side of the flywheel as opposed to 4 on the jetinetics you posted. It could be an older, different jetinetics...I'll know more when I get my eyes on it friday. Trying to to some homework before I get back home to work on it. I do plan on doing a side by side comparison with an oem flywheel.

The pic I posted is of 440/550 Jetnetics just show you the way older ones were manufactured, there’s sure to be differences between models. I’d be surprised if it’s not a Jetnetics….

 

[fastgtfairlane]

Yes and the engine held pressure. I'm going to check the carbs thoroughly, haven't yet ruled out a lean condition.

It's something that I think a lot of people don't do is a leakdown before teardown. Once a seal is broken its too late to tell if a leak was present.

The 750/800 ignition advance is alldpme through the cdi. Can't rotate the stator to advance timing. Only option is an advance plate for the pickup. The other option is a programmable cdi like a Zeeltronic a02t which works with 750/800 as well as yamaha 760 electronics.

I'd also remove the crank if it was my engine and do a thorough inspection on the crank. I've seen a crank bearing or rod bearing start to come apart and little metal particles stick to the piston and cause detonation

 

[IceRocket1286]

It's something that I think a lot of people don't do is a leakdown before teardown. Once a seal is broken its too late to tell if a leak was present.

The 750/800 ignition advance is alldpme through the cdi. Can't rotate the stator to advance timing. Only option is an advance plate for the pickup. The other option is a programmable cdi like a Zeeltronic a02t which works with 750/800 as well as yamaha 760 electronics.

I'd also remove the crank if it was my engine and do a thorough inspection on the crank. I've seen a crank bearing or rod bearing start to come apart and little metal particles stick to the piston and cause detonation

A complete disassembly has happened, my buddy tore it down last night. I'll inspect it this weekend. You can also advance the timing by rotating the flywheel on the crank without using the keyway, I've seen it done before with heaping amounts of loctite. Had to take one off of a motor and it was a nightmare, surprisingly. To my knowledge, that is not the case with this motor

 

[Big Kahuna]

Without a doubt an old Jetnetics

View attachment 450991View attachment 450993

Nope, Look at the screws on his pic..... 8 screws.

 

[mikesx]

Nope, Look at the screws on his pic..... 8 screws.

My pic is a 440/550, other than screw count looks like Jetnetics construction method…..anyone actually know what it is?

 

[WFO Speedracer]

A couple of things , you are correct every Jetinetics flywheel I have seen has four screws holding the magnets in , round holes and those timing marks , also if you will look at the 550 flywheel posted you will see the part number is stamped into the flywheel on the back side, the one on my 650 flywheel is also.

Also notice that the 550 flywheel pic he posted is of an older flywheel , it's all aluminum , look at the first pic on mine it has a steel bushing pressed in around the flywheel taper, this is because the earlier versions were prone to cracking in that area. I have one of those early 550 flywheels here , it is cracked in that area and the mahnets are bad , it works well as wall art , a paper weight or a doorstop.

If you blow up the pic of the 750-800 flywheel you will see an engraved part number on the front part of the flywheel, I can't make the numbers out exactly but it is there, not a Jetinetics.

Rad maybe , I don't remember Vidler flywheels being anodized in this color , some Rad flywheels defiantly were , I could be wrong on the Vidlers I have never seen one and most of these flywheels predate the internet.

 

[IceRocket1286]

Annnd it is a jetinetics. Must be an older version!

$100 shipped OBO if someone wants it, he’s building a stock motor.

 

[Big Kahuna]

Annnd it is a jetinetics. Must be an older version!

$100 shipped OBO if someone wants it, he’s building a stock motor.

Wait, all this and you never turned the flywheel over? Shaking my head... lol