Leak down tester

lerea3 · Post by **lerea3** » September 24th, 2011, 11:21 am

I tried searching for some pictures of a leak down tester and could not find any. Here is a picture of something I rigged up.
This is a radiator tester pump with some pvc fittings to fit the intake boot. It measures 1 5/8"

I bought 3 rubber plugs just in case I have other bike to test.

This plug is a 1 7/8" plug which expanded enough to fit the exhaust port.

lerea3 · Post by **lerea3** » September 24th, 2011, 11:23 am

Now a question for the experts. I hooked all this up and could hardly get it to 5psi. All the air was coming out of the case breather tube. Do you have to plug this hole or does this mean my rings are shoot??? I had no external leaks. Thanks Les.

100hp honda · Post by **100hp honda** » September 24th, 2011, 11:30 am

got a leak on the right side at the seal and collar or center case gasket. is it a new engine you bought ? probly be a mosquito fogger if you fire it up.

lerea3 · Post by **lerea3** » September 24th, 2011, 11:35 am

It doesn't smoke bad at all. I have no oil leaks so I know the centre case gasket is not leaking. I have only had this bike for a year and I'm not sure what the history is. Do I have to split the case to change the seal on the right side? Thanks.

Tharrell · Post by **Tharrell** » September 24th, 2011, 11:42 am

lerea3 wrote:It doesn't smoke bad at all. I have no oil leaks so I know the centre case gasket is not leaking. I have only had this bike for a year and I'm not sure what the history is. Do I have to split the case to change the seal on the right side? Thanks.

Nope. Not to change the crank seal.
If it's coming out of your tranny vent, wouldn't that be your case halves?
It wouldn't have to leak oil to be a bad sealing between the cases and yeah, that requires a split.
What engine are we talking about here?

lerea3 · Post by **lerea3** » September 24th, 2011, 11:49 am

Just looked in my manual. Just remove right side cover, clutch and primary drive gear. The breather tube comes out of the top in between the two case half. Its not leaking at the case halfs, just directly from the end of the breather tube.

lerea3 · Post by **lerea3** » September 24th, 2011, 11:53 am

AH so if the gasket on the case halfs is leaking inbetween the crank and the tranny then it would leak from the tranny breather?? Sorry, new to the engine thing. My oil should smell gas like then should it not?

lerea3 · Post by **lerea3** » September 24th, 2011, 11:54 am

its a 1992

Tharrell · Post by **Tharrell** » September 24th, 2011, 12:28 pm

I don't know about the smell but that's probably where it's leaking.
If you look at the schematic or a pic of an open crankcase you'll see it's supposed to form a sealing chamber.
Just enough room in there for the crank to go round.
You'll have to break it open to reseal it but, just for grins why don't you try to plug the vent temporarily and see what you get?

When you get ready to fix it, Dogger has done a nice pictorial here.
http://www.allthingsmoto.com/forums/f-2 ... 1-a-50432/
It's done in segments.
There's others done on this site as well.

lerea3 · Post by **lerea3** » September 24th, 2011, 1:50 pm

I am not looking forward in doing this! I can do the work myself not a problem. I know when I do open this thing up I am going to find all sorts of crap that needs changing!!

Tharrell · Post by **Tharrell** » September 24th, 2011, 3:01 pm

lerea3 wrote:I am not looking forward in doing this! I can do the work myself not a problem. I know when I do open this thing up I am going to find all sorts of crap that needs changing!!

Better to know you have a sound bike right?

Before you open it up, let some other people chime in.
I'm no master mechanic by no means.
Give it till late afternoon monday to see if some others will contribute.

Kuma · Post by **Kuma** » September 24th, 2011, 3:44 pm

Like 100hp said, could be the crank seal on the clutch side, that also leads to the trany. I have not had to change it with the motor assembled but I've heard you can by using wood screws in the flat part of the seal. You may find the method using the search feature or someone that has done may post.

lerea3 · Post by **lerea3** » September 24th, 2011, 4:09 pm

Thanks guys!!!! I think I will change the seal first then leak check it again before splitting the case. Also change the collar while I am at it.

2strokeforever · Post by **2strokeforever** » September 24th, 2011, 7:12 pm

I have not had to change it with the motor assembled but I've heard you can by using wood screws in the flat part of the seal

dont even need the screws on that side, just pull the collar out and grab it with a screwdriver

scooter5002 · Post by **scooter5002** » September 24th, 2011, 8:45 pm

An educated guess would be the center gasket. I think if the trans seal is leaking you most likely get trans oil into the combustion chamber. If it doesn't use trans oil, you are probably good. Try pulling off the trans filler cap and see if you build ANY pressure at all or still leaks out the vent tube. Got a feeling it's the center gasket. Roosty is probably the in-house expert on that stuff, see what he says. Splitting cases isn't that hard, just buy a manual and follow it. DON'T USE A HAMMER ON THE CRANK END TO SEPARATE THE CASES!! Get, or make, a puller. I use a harmonic balancer puller with longer bolts and steel plate with holes drilled in it as big washers. Works great. Order all the seals and gaskets in advance and you can do it in an afternoon.

100hp honda · Post by **100hp honda** » September 24th, 2011, 9:53 pm

dont need to call in experts from around the world to sort this out.

. my first post explained it in simple terms. its blowing through the right side or the center gasket. both scenarios go into the tranny. hard to say which is leaking. could be leaking at both places for all we know. rather than taking it apart 5 times replacing one piece at a time untill you fix the problem i would take the whole darn thing apart. lets hope for the best but dont be suprised if you find other bearings, seals, gears or shafts on the verge of going south. thats the risk you take when buying 20yo used dirt bike engines. ive been there myself and it sucks but its the price you pay to play the dirtbike game

Post by **AlisoBob** » September 24th, 2011, 11:24 pm

Kuma wrote:You may find the method using the search feature or someone that has done may post.

http://bannedcr500riders.com/board/view ... light=seal

BannedCR500Riders.com

Leak down tester

Leak down tester