Weak/low Power

[Jabber]

I recently had to do some repair due a small avalanche.
With the gas tank, seat, handle bars etc removed I decided to check the valve clearance. I did what I call the poor mans leak down test useing the hose from a compression tester. I set the piston of the appropriate cyl. to TDC and tryed to force air from my mouth thru the hose into the cyl.
To my amazement I could force my breath thru. I decided to check valve clearance because there was nothing in the way due to the necessary repairs due to the avalanche. Exahast valves were fine, the intake valves were out. I could not even fit at .0015 feeler gauge in.
Since adjusting the valve the sled has come alive. I have said for years that my rx is lacking in power. 600cc 2 strokes could easily high mark me and it was always hard starting at 5000+ ft when warm. I know of 9 other rx/apex owners that have had the same problem.
If your sled seems to be asleep or weak check your intake valves.

 

[culvert]

Good to hear about the new found power, mine is at 5500kms and seems lacking in power since I bought it a few yrs ago.

I hope everyone made out ok in the Avy! Where was it located?
I'm heading to Vale next week and seen pics of a few Avy's there this week.

Play Safe

 

[Jabber]

the avalanche wasnt big. it did bend my handle bars and lost a bit of plastic. happened last year near the end of the season in the west kootneays. I made a run up a hill that we were poking at for about a half hour, and set it off. wasnt a big deal but the advise I can give is to swim, kept me ontop.

If your down on power it could be your valves. I have compained about lak of power for 3 years before I finally checked. Feels like an extra 20-30 hp.

 

[culvert]

So how much needs to come off or taken apart inorder to do the valves?
Any special tools needed?

 

[Jabber]

I took off the seat,gas tank and side panel by oil tank. You need to drain your cooling system. You dont need any special tools. Remove the cam shaft cover and use feeler gauges to measure the clearance between the cam lobe and the bucket on each cyl. at TDC. I have a chart that shows what shim size needs to go in to get the correct clearance. I will post it tonite. A magnet comes in handy to remove the buckets that the cam lobes ride on and a magnifiying glass makes it easier to read the numbers on the shims. You will have to loosen the timing chain to romove the cam shaft. There are shims of different sizes under the buckets that you change.

If you have good mechanical ability and patience it is an easy job. Take your time and be gentle. I had the job done and the sled running in about 2 hours.

One note though, I left my spark plugs lightly screwed in so nothing could fall into the cyl.

 

[culvert]

Thanks for the info.
I just called dealer & they said 6hrs. Have to tear most of the sled down.
Well I can tear all that down myself and have no issues with doing the work myself.
It will be a good summer project.

 

[powfinger]

How many miles are were on your sled?

 

[culvert]

Jabber... did you come up with the shim chart? And is there a shim kit to buy or do you measure then order in the shims?

 

[Jabber]

I had 6000 miles on my sled before I checked the valves. I complained about the lack of power from about 2500 miles. Check your valves if you think that you are low on power. The 5 valve 4 stoke yamahas are known to need intake valve adjustment after about 1500 miles.

It took some time but I figured out how to attach a file, so here is the shim chart.

Big power difference after setting the valves. Feels like a 1000cc motor.

AWSOME

 

[Indy]

great post!

 

[culvert]

Thanks Jabber.
So do you pull apart & measure then buy the right shims or is there just a whole shim kit?

On another topic jabber.. what gearing are you running with the 162 track?
I have a 159" track & tried 19/40 gearing this wnkd in 3-4' of fresh in Valemont & sled still only pulls 95-1000 RPM. thats all it did last yr with 21/40 gearing.
Not sure why it didnt improve RPM, just means more time wasted trying to do clutching again.

 

[Jabber]

remove the valve cover then measure the clearance when the piston is at TDC. You have to remove the camshaft then the buckets to get to the valve shim. the valve shim has a number on it. Use the chart along with your clearance measurement and the current shim number to get the new correct shim required.

I run a 19/42 gear set with 8bu10 weights and a OPO primary spring. I had the EXACT same problem with rpm as you are having. It did not matter what gearing I used my rpm never got to 10500 in the steep and deep. AFTER DUE THE VALVE ADJUSTMENT the rpm is no problem, I hit 10500 all day long in the deep powder and 11000+ on the trail.

Do my cheap leak down test. Use the hose from a compression tester and try to blow into the cyl at tdc with your mouth. If you can for air thru your valves need adjustment. I bet doing my valves got me 20hp.

I hope this helps. It made a big difference for me and I am once again happy with my sled.

 

[culvert]

Well this sure sounds the same as mine. I know I was hitting alot higer MPH & RPM a couple yrs back. All new springs, clean clutches, new gearing. But just flat.

Thanks for the help.

 

[RED]

You wont likely want to buy the shim kit, each bucket shim sells for around $5bucks each. Depends on how much the dealer wants to mark them up. I can photocopy you the info & mail it to you. 1st thing, is measure all 20 valves. Then use the chart that was posted. Then pull it apart, sometimes can get lucky & just move shims around to get them all into spec. I have done couple engines now, so far had to buy couple shims for each engine.

 

[culvert]

Thanks Red
How close are you to Cold Lake?? I could have it all torn down and give ya call to come check it out with me.
But this sounds like an end of season fix. Dont have a heated shop to work in so dont want to be tearing things down with the temps we have now.

I'll drop you a PM with mail address.