86' VMAX 540 help!

[Polamaha]

Hello all, i am new to this site but have gathered LOTS of great info off of here. so lets cut to the chase, about a week ago i purchased a 1986 540K with 2400mi on it. the engine was rebuilt form the bottom up with oem parts. wasnt even ridden or broke in! i took it on a 100mile ride last weekend and it ran amazing. was running a 40:1 premix since it was its first time out, it was using oil too. then i brought it home from the lake and took it home. the next day i started it up and let it warm up for about 15mins then took off across a field and made a few laps around the yard. it was running good when all of a sudden it lost power then died and i go "oh shit, seriously!?". pull on the cord and its stuck hard. rotate clutch backwards and its free as ever then when the MAG side piston start to come up CLUNK and it stops. same thing happens when its rotated forward. got it back to the shop and took the mag side jug off and its scored along with the head and piston being pitted terribly. there is alot of slop in the rod bearing too. PTO side is brandnew shape, looks great. my question is...where should i go from here? whats the best route with the least headaches? thanx in advance

 

[killerklown]

You have to be SUPER careful with those 540's. What was the reason for the first rebuild? If was burned down before you need to find the reason and fix that, before rebuilding.
Leaking crank seals? Cracked carb boots? Uncapped carb sync nipples? Gutted/cracked airbox? Lean jetting? etc... and they won't last long.

 

[Polamaha]

reason for the first rebuild is unknown, crank seals were fine...i checked them with ether and also by flipping the choke. a tightly sealed engine will shut down imiediately if the seals are good. carb boots were checked too by spraying ether on them, they were fine. carb syn nipples!? might wanna elaborate is to what they are. airbox was completely stock and it good shape. both plugs were checked and not lean. do you have any parts?

 

[YAMMIEGOD3:16]

BUD FIRST HEAD OVER TO vintagevmax.com FOR PARTS. HAVE TO FIND OUT WHAT CAUSE THIS. TUFF HERE MAN, SOUNDS LIKE YOUR DOING ALL THE RIGHT THINGS. 3:16 (yammie tony)

 

[Polamaha]

this is my dream sled, so im going to do everything i can to make sure its running right! this is also the sled that taught me how to ride back in the day when i first started sledding so it means alot to me to finally have one. thanks for the website!

 

[YAMMIEGOD3:16]

COOL SLEDS I KNOW, LOVE MY 83. CAN,T STAY OFF IT. ALMOST SOUNDS LIKE PISTON SKIRT BROKE, DON,T KNOW. HARD TO SAY. THESE HAD INTAKE PORT BRIDGE FOR PISTON SUPPORT. MAYBE JUST WEAR AND TEAR MAN. GOT ME. 3:16 (yammie tony)

 

[Polamaha]

if anybody has a good crank laying around or a complete motor please chime in, i would like this thing to see snow again this year. also, if keeping it stock dosnt work out...what kind of engine swaps are possible with this chassis? should i post some pictures of the machine?

 

[killerklown]

Tony, what year 540's had those brass sync nipples on the intakes?

 

[Polamaha]

COOL SLEDS I KNOW, LOVE MY 83. CAN,T STAY OFF IT. ALMOST SOUNDS LIKE PISTON SKIRT BROKE, DON,T KNOW. HARD TO SAY. THESE HAD INTAKE PORT BRIDGE FOR PISTON SUPPORT. MAYBE JUST WEAR AND TEAR MAN. GOT ME. 3:16 (yammie tony)

piston skirt was what i thought, but when i took the jug off it was fine. should i post a pic of the torn down engine? and yes...i LOVE this sled!! the looks...the ride..the sound..the power..EVERYTHING!! except the engine issues

 

[YAMMIEGOD3:16]

KILLER MY 83 DOSE NOT HAVE THEM. I DO HAVE A COMPLETE 87 MOTOR THAT DOSE. 3:16 (yammie tony)

 

[YAMMIEGOD3:16]

SURE POST PICTURES. 3:16 (yammie tony)

 

[mrviper700]

likely the lower rod bearing was already damaged from previous owner, it just came apart on you. The pitting is most likely the lower rod bearings being pushed up thru trnasfer ports on top of piston then smashed into head.

its not as hard as people think to damage a lower rod bearing just lightly seizing a piston takes its toll, the detonation hammers the bearing opening up the clearances and then failure will follow because as its being run it just gets worse and worse. Unfortunately, it came apart on you, but I would guess it likely had excessive clearance when the engines topend was replaced before you got it.

be carefull running premix along with the oilpump, 40:1 is pretty rich along with oilpump, you actually lean a engine out doing that, the oil displaces the fuel and it runs leaner on the air/fuel ratio, not richer from more oil. I understand why you did it to see if the pump was working.

 

[Polamaha]

yammie, are you willing to part with the motor? and that sounds about right viper. i found shards of unknown metal in the piston and on the walls of the cyl. pics will be added in a second

 

[Polamaha]

how do you put pictures from my hard drive on here? and i dont normally run a premix with a injected sled...this was still the first tank of fuel so thats why it was that rich

 

[mrviper700]

use manage attchments when you make a post, then use the browse to find your pic files, upload them then submit at bottom.


1 note your pic files have to fit the site limits, you can resize them on your computer thru "paint" easily.

 

[Polamaha]

as you can see, mag side is pitted pretty bad. the jug is also scored up. pto side is like brandnew (first photo)

 

[opsled]

You say "rebuilt from the bottom up".

When I look at the pics I don't see that to be the case. Looking at the motor mounts and the cleanliness down in and around those areas it doesn't appear to me that the engine was pulled out. If so whoever did it didn't do a very good job. The bottom end can't be done without pulling the engine.

MrViper probably has it right with what went down here. You can clearly see vertical gouges coming straight up from the transfer ports. A bearing gone bad and/or leftover particles in the crankcase from a previous burn down can take out a cylinder very quickly. More than likely a top end was put on an already damaged lower and you were the recipient. (that sucks).

Some of the lower end parts are hard to get on these and they aren't easy to do because of the gear case that runs the water pump/oil pump. They require a bit more patience and finesse than others. If you've never done one a service manual is a must. These are very well built engines but I have found them to be more finicky with needs on workmanship when rebuilding, service and maintenance, fuel requirements and carb cleanliness than most.

I've rebuilt a few of these without issue but I have seen many with low miles and damaged cylinders. I've also seen many with close to 8000 miles that have never been apart. Fuel system maintenance and low grade fuel combinations can kill one in a hurry. The PJ carbs on them have to be right and the air box must be on or you will have problems.

You need to fully check that bottom end out and find out what the pieces are that wrecked that cylinder and where came from. Rebuilding without finding the cause is futile.

Top end parts can be found on Ebay and the guys a Vintagevmax have them too (some good deals over there). Good complete lowers are harder to get. I have two good complete 86 lowers (I still have the sleds and would have to check the mileage) and one good complete 8ON (85) engine with 2316 miles on it that has never been apart. There were a few differences in the stator over the years. 85 and up had more lighting power for grip warmers (one extra wire) and if I remember right the 87 used a different CDI (would have to check).

opsled

 

[YAMMIEGOD3:16]

WOW, REALLY BAD LUCK MAN. FIRST THING YOU HATE TO THINK THE CRANK LET GO. YOU GO TO LEAN JETTING, POOR FUEL, COLD SEIZE etc. ANYWAYS SLED IS REALLY WORTH FIXING ESPECIALLY ITS THE SLED YOU ALWAYS WANTED. vintagevmax SEND CHUCK A PM. LOTS OF PARTS. 3:16 (yammie tony)

 

[Polamaha]

i seriously appreciate all the replies!! this site is awesome! i talked to chuck and he has a few good deals on pistons and jugs. still writing everything out and trying to decide who to buy from and whats the most economical way to go as im on a very tight budget since i stuck every last $$$ into buying the machine. i will keep you guys updated as a proceed with the rebuild.

 

[vmax-540]

That looks like detonation to me, it also looks like the head has been plained as well. The carbs on that sled are side specific meaning there is a right & left as far as the jetting goes, they are stamped next to the choke plunger. Carb specs are easy to get so I would check at VintageVmax,if you can't find them I have them and would be more then happy to give them to you.If Chuck has a STOCK head I would grab that as well Yours really looks like it has been plained.. Any Vmax I have seen have had those brass ports on the intake port ,just like the 81 SRX