Engine

 

Engine Fitness - Engine has high miles. COLD VS. HOT - Compression check? 
Engine Fitness - Refresh your pistons/rings (Big John) 
Engine Fitness - Leakdown test "engine compression" what does it do?
Exhaust - Muffler caused engine speed change
Jetting - Engines of higher rpm than stock

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Engine Fitness - Engine has high miles. Compression check?
Question) My sled has about 6000 miles on it. What can wear, what can I look for?

Answer) With 6000 miles on your sled, how many miles does engine have? I want to know what kind of shape your piston rings are in. If your rings and pistons are worn out then it will be difficult to calibrate the clutch kit.  The settings will work good when the engine is cold but when engine hot, then will not run good and lowering engine speed as a result.  This could be an indication of the piston rings or complete piston needs to be changed.

Take a Cold vs. Hot compression test.
1] Start the sled and let it run for about 30 seconds and kill engine.
Put the compression gauge in the cylinder head and take compression with 5 PULLS WITH WIDE OPEN THROTTLE.
What are the values?  (record the values)

2] Start the sled and let it run until the coolant is at operating temperature and flowing.  Test the coolant temperature with your hand by touching the tunnel heat exchanger.

To achieve this operating temperature in a place where you cannot go ride the sled, "Remove the drive belt" so you do not burn any of the cogs in a localized area of the belt while the belt rubs on the clutch shaft.

OR, go take it for a run if you can and out there when engine operating temperature, shut it off and check the compression with 
5 PULLS WITH WIDE OPEN THROTTLE.
What are the values?  (record the values)

It does not matter if your gauge is accurate or not as long as you use the same gauge when cold vs. hot temps.

Indications of poor rings
cold compression - 5lb(35kpa) or greater difference from mag to pto.
Hot compression - 7lbs (48kpa)(or more less than when it was cold then you need rings.
Hot compression - 10lbs(68kpa) or more less than when it was cold then you need pistons.

Example:
Cold @ 145lbs (999kpa)
Hot @ 138 lbs (951kpa) or less than...
Value difference more than 10lbs (68kpa)

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  Engine Fitness - Refresh your pistons/rings

One thing I been stressing is if owners of sleds from 02~05 are keeping their sleds or owners with any 600/800 engine that has around 5000 miles, then check the engine compression cold vs. hot and ensure the engine is fit before you move forward and get a clutch kit.  It’s tough to calibrate a kit or make a consistent clutch setting when the engine gets hot and compression values lower.
You will observe correct rpms when running cold or warm but as the engine gets hot, may observe rpms drift low;  an example the engine runs 200 rpms lower at full throttle due to failing compression. (as vehicle speed increases)

If keeping the sled, then it is an "Investment" to freshen up the top end of the engine.  Run the best piston you can for long life and that is usually the original BRP piston.

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Engine Fitness - Leakdown test "engine compression" what does it do?
Cylinders never wear even as you know. Therefore, you will have minor deviations in the walls of the cylinders and as a result less ring seating occurs. The piston speed makes up for this deficiency as it passes the offending area quickly. Even with plated and SCEM (Boron Composite) cylinder walls that literally as hard as diamonds, you have these offending areas.
The leakdown test finds offending areas on the cylinder walls and can show the truest measurement of ring fitness.
It shows if pistons need to be replaced?...could be skirt collapsing?

Yes, of course...look in the corners where the skirts start and see if you witness and microscopic cracks. A magnifying glass helps as these a very tiny and often not able to be seen with the naked eye.
Your Big Bro, Freddie Klies
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Exhaust - Muffler caused engine speed change
Question) I put on this XXX can and I lost top end speed, what happened?

Question) I put this XXX can on and I lost peak rpms, what happened?

Answer) Sometimes an aftermarket muffler does not have the correct "choke" to cause the engine to run at its rated speed.  I personally had a muffler installed that lost 1300 rpms at 10000 feet in Cooke City MT.  I put the stock muffler back on and 8000, put a different muffler on and 8000 rpms.  Put my muffler back on and 6700 rpms.  Put the stock muffler back on and 8000.

When running the engine at full throttle, the exhaust pipe itself will see say 4.0 psi internal pipe pressure.  When there is a change in your sled performance (lowering power and engine speed) the internal pipe pressure would be lower - 3.9, 3.8 psi, etc.

My advice to people who buy muffler "cans" - don't get rid of your original stock muffler, just in case you need to use it again.

When going from low elevations to high elevations for the first time with your aftermarket muffler - always take your stock muffler along with you to the mountains to be able to rule out a muffler being part of an engine speed problem.

I have personal first hand knowledge that after putting a "tuned" muffler on, this 2014 800etec x 163 seen low peak engine speed.  Regardless of clicking up the calibration screw on the primary clutch to increase engine speed - the engine just got more lazy.  Put the original muffler back on and clicker back to original position and power by the hour 7900~8000.

Not all mufflers do this - this is information to help you sort out an engine speed problem to rule out a muffler contributing to low peak engine speed.


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Jetting for engines of higher rpm than stock.
Engines that use high rpm pistons or are high rpm big bores;  to get the engine with these mods to run at their full potential 8300~8500, the tuner has calibrate the carburetor jetting correctly for the engine to start to make correct combustion temperature to reveal the potential power the engine has after the rings are broken in.


If the engine is rich, it won’t run at correct rpm, the tuner will observe low rpms.  A common rpm for a rich engine to run at will be near the rpms of peak torque which can be from 250rpm to 450 rpms low of the actual potential peak hp rpms.  An example 8400 rpm engine with rich jetting calibration can run at 8000~8100.  Once the tuner starts to get the jetting correct for the engine then the rpms will start to want to turn higher rpms.
I only recommend jetting with a borescope, like the PV-618 .  The borescope is not a cost, its an investment.  You learn to use this scope and jet calibrate wisely, nobody will ever tell you how to jet an engine, you will tell them how.
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Thanks to: Al Shimpa, Freddie Klies and Dallyn Maxwell for jetting information.

Don’t be fooled by more hp = more flyweight because if the engine is making hp at a higher rpms then you won’t want to change the flyweight.
Run the engine first, dial the jetting in then start to spend a dayride to get the flyweight dialled in if-needed.

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