Other Xlt1200 keeps melting pistons

If you give me more info on exactly what has been done as far as choke plate removal and cat removal I can probably be of more help.

Running that at 32/1 was a mistake with stock jetting.
The ski is bone stock. Has choke flaps still, has the cat, has stock airbox. For this repair though I plan to remove the cat and do a d plate, reinstall the oil pump, and do some after market flame arrestors. Maybe a 122.5 main and 110 pilot?
 

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
I am thinking your cat is partially plugged up, this makes it retain heat and skyrockets the Exhaust gas temps melting down the pistons, never ever rebuild one of these without deleting that crap, Yamaha knew it wasn't going to work before they did it, they went through the exact same scenario in the RD350LC motorcycles, cats stopped up taking the top end with it.
 
Stock jetting is part of your issue, it's way , way too lean , by running premix you have leaned it out even more., if the choke shafts have been removed it has to be rejetted see below and don't try to rejet it using the O-side specs and the stock airbox , it won't work and no one has been able to make it work..for stock airbox follow the first set of specs but to use them the cat converter has to be removed which if it hasn't been already it's part of the problem. They retain too much heat and melt things in a bad bad way .

Myself is correct those 800's and 1200's are like a Swiss watch , they will not tolerate any imprecision . He is also spot on about debris, anytime a reed valve motor pukes , you have to pull all the reeds out and clean out the debris, if you don't as soon as you fire it up it goes right back through the engine, I know it's a pain to do on these but this is what happens when you don't.

I don't use those SBT cylinders they are crap , they don't dissipate heat like the stock cylinders do , cast iron retains heat , Aluminum dissipates heat , these engines were designed with plated cylinders for a reason, they ruined them when they installed those thick cast iron liners in them., the heat dissipation is so bad that they have to use a lot of extra piston to wall clearance to keep them alive probably double what the stock clearance is and they rattle like a freight train , absolute junk IMO.

The following was copied from Bamafreeride where I store important info like this :

Bit off topic but if anyone is ever wanting STANDARD European spec carb settings they are as follows. I have given myself a headache trying to source these but I have had them confirmed from 2 x Yamaha dealers in the UK
Main Jet 135
Pilot Jet 92.5
Low speed Screw carb 1 = 1 1/4 carb 2 = 1 1/2 carb 3 = 1 5/8
High speed screw Carb 1 = 7/8 carb 2 = 3/4 carb 3 = 7/8

The european specs skis have a decat plate from factory, no exhaust temp sensor and no plastic cover over the stinger.
The are set up differently from USA Skis.

Oside Bill jetting specs

1200R Aftermarket F/A's (Flame Arrestors) chokes intact

110 Pilot jets, 1 turn out on low speed adjusters
120 main jets, 1-1/2 turn out on high speed adjusters
1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off pressure.

1200R After Market F/A's chokes removed.

110 Pilot jets, 1 turn out on low speed adjusters.
125 Main jets 1-1/4 turn out on high speed adjusters
1.5 Needle and Seat, 95 gram spring (Dull Silver) 42-45 avg. pop-off
With aftermarket flame arrestors it’s assumed the cat is removed too right?
 

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
All those jetting specs are with the cat removed, it's damn foolish and irresponsible to leave it in there knowing that sooner or later it will fail.
 

Myself

manic mechanic
Location
Twin Lakes AR
One single 1200 power valve setup has ever left my shop without D-plate and chip. The customer had bought an 800 and 1200 brand new and wanted them to stay oem spec. I installed a new old stock oem converter for him.
 

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
I did it once, you know what happened the cat went out a couple of months down the road , the customer wanted me to cover the repair for free, never again if they don't want me to fix it right then come pick it up and try someone else, there are plenty of jacklegs out there that have no problems doing half assed repairs. I assure you.
 
Have you done a leak down test on the engine before disassembly to verify no air leaks? Or after reassembly? It is absolutely a necessity to do a leak down before teardown to verify there was no air leak anywhere.
 
I did it once, you know what happened the cat went out a couple of months down the road , the customer wanted me to cover the repair for free, never again if they don't want me to fix it right then come pick it up and try someone else, there are plenty of jacklegs out there that have no problems doing half assed repairs. I assure you.
Hi WFO Speedracer a customer has dropped a Yamaha XLT1200 in with a seized engine on number 3 cylinder and starting to seize on number 2 I have the engine disassembled now and would greatly appreciate your help if there is a way of messaging you with more information?
Nobody this side of the water seems to know anything about them or want to touch it.
Thanks
 

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
Just started work on one yesterday with no compression on the middle cylinder , you can bet your sweet a$$ that isn't a crank seal issue at least , also the oil pump was deleted so it's not or at least shouldn't be an oiling problem, that leaves two things , either it dropped a power valve or it melted because it still has the Catalytic converter in it and it is stopped up, not letting the exhaust heat get out.. I will know more later today . Either way the Cat goes bye bye , it gets a chip in it and the carbs get rejetted with choke shafts removed and Pro K filters because that is the way the guy wants it set up, these are one of the few sitdowns that I recommend removing the choke shafts on ,, mainly because it's not going to crank well with the choke anyway you slice it .

Anyway Aughrim here is my suggestion , make a new thread and I will walk you through it there as best I can , while I don't mind walking you through it via text or email, that only benefits one person whereas a thread at least has the potential to benefit many people.

Also others might chime in with insights that I have either overlooked or don't have.
 
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I have also seen water cause that kind of damage on a piston. If it's getting by the head gasket it boils on the piston and causes pitting. Polaris triples were famous for doing that. They were also famous for throwing a crank out of phase with very little effort. When I worked with Polaris we had about a dozen cranks go out of phase from brand new skis like the Genesis and Virage to just new rebuilds like the SLT 780. I wasn't well informed on the exact reason why their cranks were so prone to going out of phase but I definitely saw a lot of unhappy customers as a result of it. Water injestion was definitely one reason for it though. The slightest bit of water in the carbs from a flip over and the probability of a crank being spun out of phase was very high.
 

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
I have also seen water cause that kind of damage on a piston. If it's getting by the head gasket it boils on the piston and causes pitting. Polaris triples were famous for doing that. They were also famous for throwing a crank out of phase with very little effort. When I worked with Polaris we had about a dozen cranks go out of phase from brand new skis like the Genesis and Virage to just new rebuilds like the SLT 780. I wasn't well informed on the exact reason why their cranks were so prone to going out of phase but I definitely saw a lot of unhappy customers as a result of it. Water injestion was definitely one reason for it though. The slightest bit of water in the carbs from a flip over and the probability of a crank being spun out of phase was very high.
Yep first thing I did on a Polaris triple was run the center to TDC then run a vernier caliper down the two other spark plug holes till it touched the piston, if they were not the same reading it meant it was crankshaft time.
 
Just started work on one yesterday with no compression on the middle cylinder , you can bet your sweet a$$ that isn't a crank seal issue at least , also the oil pump was deleted so it's not or at least shouldn't be an oiling problem, that leaves two things , either it dropped a power valve or it melted because it still has the Catalytic converter in it and it is stopped up, not letting the exhaust heat get out.. I will know more later today . Either way the Cat goes bye bye , it gets a chip in it and the carbs get rejetted with choke shafts removed and Pro K filters because that is the way the guy wants it set up, these are one of the few sitdowns that I recommend removing the choke shafts on ,, mainly because it's not going to crank well with the choke anyway you slice it .

Anyway Aughrim here is my suggestion , make a new thread and I will walk you through it there as best I can , while I don't mind walking you through it via text or email, that only benefits one person whereas a thread at least has the potential to benefit many people.

Also others might chime in with insights that I have either overlooked or don't have.
Thanks WFO Speedracer for the advice, i will post a new thread there now with pictures. Hopefully it will benefit a few.
 
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