2013 YAMAHA MOUNTAIN MAX 600 TWIN PROJECT SLED

• THE GOAL, GET HER RUNNING WITH OFF THE SHELF PARTS.

• ASSEMBLE THE SLED WITH COMPONENTS THAT WILL INCREASE THE SLEDS LIFE EXPECTANCY.

• END UP WITH A SLED THAT HAS LARGELY UNKNOWN EXTREMELY RESPONSIVE CALIBRATION FEATURES.

This 600 twin is *estimated to have about 3% more HP than the 94 HP version in the 1996 models. This Mountain Max is published to weight about *505 Lbs.. The track is a 136 x 15 with an advertised 1.5" lug. This sled's reasonably short track and all temperature responsive 97 HP mill make it a great trail breaker thru the tight NISBET FOREST trails.

*Source winter 96/97 RACE & RALLY magazine.

 

Looking as bought years ago for parts

THE ENGINE WAS PARTLY SEIZED
When the snowmobile was acquired for parts. It did not turn over very well. A little water sitting in the cases did damage other bearings as well.

Upon disassembly the seal fell apart and was rusted.

One of the PTO bearing is welded together then rusted for good measure.

The outside PTO bearing fell off the inner race which was heavily scored.

Side by side,
 with a crank ready to go.

Our spare crank was looked after and checked out by The Crank Doctor.

 LOOKING FOR THE CAUSE OF FAILURE
After seeing the damage and noticing that she's been apart and repaired before we look for the cause of the the bearing failure and minor piston seizure. We discover a worn oil pump drive.

In the above photo the oil pump drive is supposed to look like this.

The above 2 photos are of a worn out failed oil pump drive, the rectangular drive was rounded off by the interfacing female water pump drive's millions of pulsations of a twin cylinder engine. So oil pump failure is the cause of the engine damage. It likely failed then the resulting overhaul was short lived because the oil pump wasn't checked. Had they added oil to the gas then monitored the oil injection oil usage they could of caught this with out any disassembly for examination.

The oil pump is driven from this coupler on the back of the water pump, the pair is belt driven off the MAG side under the recoil housing.

  OTHER DAMAGE

This is what the dowels look like. The engine is supposed to be assembled carefully lining all the dowels up with the bearing races as you set the crank into position and torque the cases together.

This dowel was not lined up and the previous owner/repairer torqued the cases back together as is. The misaligned dowel was pressed thru into the crankcase.

  CRANKCASE REPAIR and ENGINE ASSEMBLY

We take a used and unusable 600 twin crankcase and drill some pilot holes which will help us predict the drilling outcome.

We start with a small drill bit.

The small drill bit came thru right next to the dowel. Now we drill with a much larger bit, this way we can catch the edge of the dowel.

Then using a small pin punch we drive the dowel back into position.

The holes are filled with epoxy which should seal up the lower crankcase from any leaks. 

In this photo you can see some damage to the cylinder base gasket surfaces adjacent to the rod area. The surface was beaten on enough to leave a raised lip where the cylinder base gasket sits.

This is starting to look like an engine.

This is the baked on reflective piston top coating. See SIDE BAR:  *2

The pistons are not coming out of the hole so we don't suspect anyone has machined the jugs down.

The PTO side cylinder was close to like new.

The exhaust manifold is lightly attached before torquing the cylinders all the way to the cases.

The Smart Carbs sure have a lot of sensors and connections. See SIDE BAR: *3 

SIDE BAR: *1 this  baked on ceramic coating on the skirts is designed to make the piston extra slippery resulting in less heat transferred into the water jacket thru the cylinder walls. The thickness is negligible, in fact with a cooler running piston it is likely going to requiring less clearance. The theory being less heat in the piston less expansion.

SIDE BAR:  *2 The baked on polished reflective quality of the piston top coating is designed to keep more of the heat (read energy) in the combustion chamber where this unspent energy is used to push the piston down, resulting in a greater force, or horse power and torque, and at the same time prevent the piston and wrist pin area from reaching the same high temperatures from repeated firing every stroke and dual compression action on every stroke, like a 2 stroke has.

SIDE BAR:  *3  The SMART CARB set up was used on Mountain Max 600's from 1996 to 1999. In 2000 the 600 Mountain Max was a triple and did not have SMART CARB. There was however many years of 600 twin Ventures equipped with the SMART CARB.

ENGINE INSTALL AND FIRE UP

Time to make the final connections to the oil pump and fuel pump line before we set her in all the way.

The engine is sitting where she belongs.

The carbs get connected.

The basic familiar liquid cooled  Yamaha twin lay out used from the mid 90's for about 10 years.

This ring gear was one of the main hold ups on the whole project. See SIDE BAR: *4

SIDE BAR: *4  This was one of the main hold ups on the whole project. The harmonics (best guess) on the Yamaha 600 twin must play a part in their reliability factor. We have torn down (not exactly the procedure) many 600 twins with broken rods and cranks. Often the resulting damage has actually cut the engine completely into 2 halves. A tear down is not exactly what I would describe, removing the head and tossing the rest in the garbage! We have put 80,000 to 100,000+ Km's on Yamaha 500's without such a failure and they are exactly the same cranks. Sure we have had a couple fuel related engine failures over the last 20+ years, but none were like the catastrophic failure as seen in the 600's we've wrecked for parts. The failures with 500's that we have experienced could be counted on one hand and they were all fuel related except one (** SEE BELOW). In discussion with many factory trained Yamaha mechanics a pattern emerged. This type of failure had not been seen in a well serviced 600 twin that was equipped with electric start. It has been suspected that the addition of the ring gear on the clutch smoothed out the harmonics present. We waited until a ring gear dropped into our lap for our Yamaha 600 twin project. The following snaps are representative of several 600 twins I have salvaged over the years!

SIDE BAR:  *6  The sled smoked a fair amount because oil had also been added to the ethanol, but overall the sled ran exceptional for the temperature. She snapped to just a hair under 8000 RPM and hauled to 120KM right now. The sled was responsive and was exceptionally responsive for this temperature. Credit must be given to this 4 year wonder "SMART CARB".

SIDE BAR:  *7  The used plugs that we pulled out of it after 8 or so KM's were actually starting to tan, the electrode was a bit shiny so the extra oil must be playing a part. I fully expected to see some pretty dark plugs even with the sled running so well. The wait for next winters conditions will be the next step.

We get to put this 600 to work with a few more modifications.

• 16-02  We hit the off the beaten path route around Nisbet!

• 14-11  Running wide open thru the fields!

• 14-06 A cross country surprise

• 13-17 A quick ride down route 66 to test her out.

NOTE: Except a pair of handle bar hooks we have completed our 2013 Project sled  transformation from Bush Whacker to 

 Prairie JACK 600 136

So I did out some old scales and check...what does she   weight?

 SNOCRUISE TOUR  SLEDS

 TECH 101 INDEX

 Snocruise snowmobile  EVOLUTION

Parked on the North Branch.

NOTE: The 500cc and 600cc twins from 1997 up shared the same crank and cases, in 100,000 and more of 500's on the snow never had a failure like all the 600 twins we have seen.

**In rental situations the very few 500 failures we had, were all directly after the rental customer had gassed up at a fuel station. The following is the exception.
 
-In one isolated RENTAL case a 500 engine's prefilter was not cleaned in very snowy conditions, negligently allowing the filter and intake tract and to completely plug solid with snow. This event suffocated the entire air intake system, stalling the engine (seizing the engine) numerous times. (the engine was actually seizing up, 2 strokes don't stall at 8000RPM!)
Waiting for the seized engine to cool down
(really waiting for the pistons to shrink so it would turn over,
the piston crown and rings were 100% intact)
The dash mounted intake prefilter that was solidly packed with snow had turned into a solid  block of ice, 30" wide x 4" deep. During this transformation water then replaces the oil as a substitute for lubrication between the piston skirt and the cylinder. Then the engine was forced to restart after seizure, cool down and after seizure repeatably until their was nothing left. It is interesting to note that we have never had an engine issue in 20 years "While on Tour", hmmm...seriously! And if you have followed our Youtube videos   you will see they are run hard cross-country, this would be the second toughest work out next to the mountains.