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DIY Leak down test.


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#1 HCSA Rev Rider

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Posted 17 November 2008 - 12:42 PM

WHAT?? A leak down test is a compression test in reverse. Instead of measuring the ability of the engine to create pressure, we want to check it's ability to hold pressure.

WHY??? An engine that has an air leak is an engine that can suck air when running, sucking air usually = burn down. Other symptoms of air leak, hard to hold a steady idle. Also and maybe more importantly this test can tell you if your inner crank seals are leaking. If your inner crank seals leak the ISOFLEX(info) grease that lubes the bearings can be lost into the engine which will lead to bearing failure. See potential $$$$ expensive mid-season repair.

You can make this leak down kit from parts at the hardware store. see pic. We (fossil99ca) got everything at Canadian Tire here in Canada.
Drill small holes in the cap to insert rubber tire stem and pressure gauge fitting. Carb boot plugs pictured are 2 pieces that thread together, use silicone on threads and tighten down hard. They fit snug into V-Force boots.

Edit: Guage we used does both vacuum and pressure, maybe this will help locating one. See pic. This Equus 3620 Vacuum Gauge will work.

Note: you can doo this test with engine in machine..these pics were taken before I put my engine back in, wanted to make sure 100% my redone crank was good before putting it in.

Simple steps
1. Plug the y-pipe
2. Plug both carbs
3. Pinch impulse line.
4. PTO elbow cap on at first to find other leaks, remove cap if able to hold 5psi.
5. If powertek engine plug extra case line..see pic
6. Spark plugs should be installed

Using a bicycle pump try to and pressurize to 5 psi...don't over do it, you don't want to blow out any seals. Most likely your first attempt you will not be able to hold any pressure. Here are all the areas we found most common to leak. Use a spray bottle with soapy water, leaking air will cause bubbles. Seal all problem areas and re-test. I had to get my y-pipe welded this year.

Common leaks
y-pipe is split at seam.
y-pipe gasket seal leaking...see pic to seal
rave valve gaskets leaking...a little grey gasket maker if tighter doesn't work.
Impulse line is not pinched off perfectly.
Carb boots are rotten and leaking. Very common.
Carb boot plugs are not tight enough.
Base gasket is leaking...sucks when this happens. I don't know of a way to temporarily seal it without a tear down.

Test #1. If you can hold 5 psi for 10 mins with the PTO elbow cap off your inner PTO & MAG bearing seals are good.
If air passes through the PTO elbow your inner PTO seal is leaking. There are varying degrees of inner seal leaking, slow leak means it hasn't failed completely but you are on borrowed time. Holding no pressure at all and the seal has completely failed.

Note: If you can't hold pressure but there is no air leaking from the PTO elbow your MAG inner or outer seals are leaking.

Test #2. If inner seal is leaking you can put the cap back on and test again, this will test the outer seals ability to hold pressure. If you can hold pressure with cap on at least you know you won't lean out a piston if you decide to run knowing your inner seal is leaking. How long until all of your ISOFLEX is gone is anybodies guess.

Ok so now you have determined your crank is doomed and you want to yank it before it leaves you dead on the trail? Sleddude5's DIY teardown threads are HERE. Goodluck.

Attached Images

  • Leakdown_test_kit.jpg
  • Carbs_Plugged.jpg
  • Guage.jpg

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#2 HCSA Rev Rider

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Posted 17 November 2008 - 12:43 PM

... Close-up of a bicycle tire valve stem...some are having trouble locating/installing this piece.
Posted Image
Posted Image

Attached Images

  • 5psi.jpg
  • Impulse.jpg

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#3 HCSA Rev Rider

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Posted 17 November 2008 - 12:44 PM

PTO Elbow/nipple

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  • Nipple.jpg
  • ypipe.jpg

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#4 HCSA Rev Rider

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Posted 17 November 2008 - 12:46 PM

Bad inner PTO bearing

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  • Inner_PTO.jpg
  • Plugs.jpg
  • Main_plug_Diameter.jpg

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#5 HCSA Rev Rider

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Posted 17 November 2008 - 12:52 PM

PowerTeks only

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#6 scha0786

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Posted 17 November 2008 - 12:57 PM

where can you buy this permatex ultra copper silicon?

----12' Polaris Pro RMK 600 155"----
custom made gas rack
retro logo mud flap
----06' MXZ Renegade X 800 Ptek-----
sway bar removed
136x1.75x16 stocker track
scratchers --- digital temp gauge
MBRP silencer
summit 6.9 pilots/summit riser
westach EGT gauge
jc's custom vents (sides/top)
Big John built motor
DJ dual elevation kit
WRP snow eliminators
---06' GSX 500ss (Wife)-----
digital temp gauge -- SPI Ypipe


#7 HCSA Rev Rider

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Posted 17 November 2008 - 01:46 PM

where can you buy this permatex ultra copper silicon?


Canadian tire in Canada, most auto parts stores should have it in the US. Napa?

2015 Renegade XRS 800

 

Winter 06 vid Machine Head
Winter 06 vid What a RUSH
Winter 06 vid Helmet Head
Winter 06 vid Helmet Head pt.2
Winter 06 vid ZZ Top Trails
Winter 07 warm-up Are You Ready?
Winter 07 Paudash Trail Blazers Launch vid Time to Fly
Winter 07 vid Rear View Mirror
Winter 08 vid Lake & Trail Cruising

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#8 canadoo

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Posted 17 November 2008 - 01:48 PM

where can you buy this permatex ultra copper silicon?

any hardware store should have it



Great thread!!!

I put together a tester as well and didn't get more than 5 seconds into it when my Y pipe made a lot of noise.. I had a bad seal there and an unoticable crack in the Y pipe itself.

everyone should do this test at least once a year!!!

#9 Mac-Daddy

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Posted 17 November 2008 - 02:57 PM

Nice way to test the Y pipe. Normally you would test with exhaust flange blocked off. Now I need to buy more stuff and set it off to the side of the shop.....

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#10 scha0786

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Posted 17 November 2008 - 05:00 PM

When you guys pull the y-pipe off do you buy new bolts from BRP (intergrated lock tite), and new gaskets. In addition to that do you still put a little bit of the copper silicon inbetween y-pipe and gasket and gasket to motor to help keep things sealed up?

By the way I checked my shop manual and it states that the motor only needs to hold 5psi for 3 minutes. this was for a 2006 ptek motor though.

don't forget to torque the y-pipe bolts down to 97 in-lb starting in the center and working your way out.

----12' Polaris Pro RMK 600 155"----
custom made gas rack
retro logo mud flap
----06' MXZ Renegade X 800 Ptek-----
sway bar removed
136x1.75x16 stocker track
scratchers --- digital temp gauge
MBRP silencer
summit 6.9 pilots/summit riser
westach EGT gauge
jc's custom vents (sides/top)
Big John built motor
DJ dual elevation kit
WRP snow eliminators
---06' GSX 500ss (Wife)-----
digital temp gauge -- SPI Ypipe


#11 HCSA Rev Rider

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Posted 17 November 2008 - 05:05 PM

When you guys pull the y-pipe off do you buy new bolts from BRP (intergrated lock tite), and new gaskets. In addition to that do you still put a little bit of the copper silicon inbetween y-pipe and gasket and gasket to motor to help keep things sealed up?

By the way I checked my shop manual and it states that the motor only needs to hold 5psi for 3 minutes. this was for a 2006 ptek motor though.

don't forget to torque the y-pipe bolts down to 97 in-lb starting in the center and working your way out.


I did replace my y-pipe bolts this time because they were starting to round off due to the use of the ball-end allen wrench. ( 0.70c each at crappy tire) Note: I reinstall with a dab of blue locktite and nordlock washers just to be safe. These bolts are known for backing out mid-season.

Yes to silicone on both sides of gasket..just a thin layer no need to go crazy, you just need it sealed enough to hold 5 psi so you can test the negine.

2015 Renegade XRS 800

 

Winter 06 vid Machine Head
Winter 06 vid What a RUSH
Winter 06 vid Helmet Head
Winter 06 vid Helmet Head pt.2
Winter 06 vid ZZ Top Trails
Winter 07 warm-up Are You Ready?
Winter 07 Paudash Trail Blazers Launch vid Time to Fly
Winter 07 vid Rear View Mirror
Winter 08 vid Lake & Trail Cruising

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"Arguing on the internet is like running a race in the special Olympics even if you win you're still retarded."


#12 scha0786

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Posted 18 November 2008 - 08:11 AM

sounds good thanks

----12' Polaris Pro RMK 600 155"----
custom made gas rack
retro logo mud flap
----06' MXZ Renegade X 800 Ptek-----
sway bar removed
136x1.75x16 stocker track
scratchers --- digital temp gauge
MBRP silencer
summit 6.9 pilots/summit riser
westach EGT gauge
jc's custom vents (sides/top)
Big John built motor
DJ dual elevation kit
WRP snow eliminators
---06' GSX 500ss (Wife)-----
digital temp gauge -- SPI Ypipe


#13 HCSA Rev Rider

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Posted 20 November 2008 - 07:15 AM

ttt

2015 Renegade XRS 800

 

Winter 06 vid Machine Head
Winter 06 vid What a RUSH
Winter 06 vid Helmet Head
Winter 06 vid Helmet Head pt.2
Winter 06 vid ZZ Top Trails
Winter 07 warm-up Are You Ready?
Winter 07 Paudash Trail Blazers Launch vid Time to Fly
Winter 07 vid Rear View Mirror
Winter 08 vid Lake & Trail Cruising

-----------------------------

"Arguing on the internet is like running a race in the special Olympics even if you win you're still retarded."


#14 mxzeatr

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Posted 20 November 2008 - 08:05 AM

I PM'd a link to SledDude5 and this has been added to multiple FAQ sections on the site.

Thanks for the write up!

#15 HCSA Rev Rider

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Posted 20 November 2008 - 10:15 AM

I PM'd a link to SledDude5 and this has been added to multiple FAQ sections on the site.

Thanks for the write up!


Cool..good idea mxzeatr.

One more usefull pic..

Y-pipe removal made easy. 5mm ball end allen with extension. No more cursing the y-pipe removal.

EDIT: PRINCESS AUTO in Canada sells this kit.

Attached Images

  • Ball_end_allen.jpg

2015 Renegade XRS 800

 

Winter 06 vid Machine Head
Winter 06 vid What a RUSH
Winter 06 vid Helmet Head
Winter 06 vid Helmet Head pt.2
Winter 06 vid ZZ Top Trails
Winter 07 warm-up Are You Ready?
Winter 07 Paudash Trail Blazers Launch vid Time to Fly
Winter 07 vid Rear View Mirror
Winter 08 vid Lake & Trail Cruising

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"Arguing on the internet is like running a race in the special Olympics even if you win you're still retarded."