Compression tester Q

[Whitty21]

I know the down fall of a compression tester over a leakdown tester is that the compression tester doesn't do the bottom end, but will it tell me if the reeds are leaking? i am trying to get a hold of holeshot for one but i was wondering if a compression tester would do the job this time?

 

[sicivicdude]

A leakdown tester doesn't test the reeds either...

The leakdown tester like holeshotman sells plugs the exhaust port and carb hole and pressurizes the entire engine. The reeds are included but not specifically tested.

The reeds aren't designed to hold against pressure. They are simply a flow check valve. The only check reeds really get is visual. If the reed petals are cracked or splintered or the petals don't sit flush against the frame, it's time for a new set. Or if you are in doubt, throw them out! Boyesen power reeds are cheap to replace. If you're ballin' on a budget, get vito's dual stage. I'm running a set right now and they're doing fine.

 

[Whitty21]

Sorry I meant the reed cage gasket, from what I have hearsd they are prone to leaks when you take it apart

 

[sicivicdude]

A compression tester will not check the reed cage gasket but a leakdown tester will. Those gaskets are prone to leaking. Apparently worse on some reed cages than others.

The only thing I can tell you was my personal story on that. Knowing the reed cage gaskets are prone to leaking I purchase some K&W copper seal (aviation shellac to some) and did the thinnest coating I could manage before I applied the gasket to the cylinder boss. I then hurriedly installed the reed cage and manifold and tightened them down. I now have a single kick cold start blaster with a consistent idle.

Now the reed cage gasket may be a pain in the butt to get off but that's why they made straight razor blades and roloc pads...

 

[super noober]

i use a gasket on every mating surface with mine too, one against the cylinder then one between the rad valve and my intake. its a pain in the ass to get everything lined up but worth in IMO

 

[sheeblast]

ya i dont a gasket between reeds and jugs, then i use yamabond between reeds and intake.
a little layer of yamabond or something like it does help with mating surfaces.

 

[Whitty21]

What is yamabond actually, like I know what it is, but what is it called so I can try to find something like it, cause I can't seam to find it around here, is there another brand to look for?

 

[sheeblast]

it is called yamabond, your local yamaha dealership should have it.

http://store.58cycle.com/product_p/yam sealant.htm

 

[Whitty21]

it is called yamabond, your local yamaha dealership should have it.

http://store.58cycle.com/product_p/yam sealant.htm

I know what it is, I was kinda looking for the chemical name. The closedt dealer to me doesn't carry it but there is another I can call and ask, does anyone know of any other products?

 

[sheeblast]

yamabond is the product and chemical name

permatex RVT sealant is close to the same thing but not as good.

 

[Whitty21]

yamabond is the product and chemical name

permatex RVT sealant is close to the same thing but not as good.

Thanks man, I will keep it in mind. So does a compression tester just check the wrings and head seals?

 

[sheeblast]

yes it only checks for that.
leakdown tester checks for any leaks in the system you are checking, like if you take off the carb and plug it there and plug your exhaust port, it will check your complete engine.

 

[Whitty21]

I intend on getting one from holeshot, tried finding parts for making my own n but apparently canadian home depots are differen, and it was gunna cost more than buying from holeshot. I am just gunna use the compression tester this weekend and yamabond the reed cage, I only had the head off, so other than the reed cage I shouldn't need the leakdown tester, I still want one though

 

[sheeblast]

it is always good to have, you never know where you might have a leak.
and all you need to make a leakdown tester it some PVC pipe that fits your intake boot, and it need to be capped off, and an expansion plug for the exhaust port.
then you get a valve stem to put air in and a cheap PSI gauge.


also dont ever use yamabond or anything like that on the head gasket with a liquid cooled engine.

 

[Whitty21]

it is always good to have, you never know where you might have a leak.
and all you need to make a leakdown tester it some PVC pipe that fits your intake boot, and it need to be capped off, and an expansion plug for the exhaust port.
then you get a valve stem to put air in and a cheap PSI gauge.


also dont ever use yamabond or anything like that on the head gasket with a liquid cooled engine.

I had everything except the shrader valve and guage, the cheapest guage I found was $17 and I couldn't find the proper shrader valve, which I prolly could have, but I just said piss on it and I will talk to holeshot

Out of curiosity, explain the liquid cooled part just to enrich my knowledge

 

[sheeblast]

like on a banshee, if you put yamabond or something on the headgasket it can get into the water jacks and clog them up causing it to blow up.

but what is a shrader valve. i just used a valve stem you would find on your quad. and the gauge, i got mine from a harbor freight, it was only a couple bucks.

 

[Whitty21]

It is a fancy name for tire valve, I jusy got lazy abd that makes sense about the liquid cooled too, thanks man!!!!!

 

[sicivicdude]

schrader valve is the technical name for the valve system used on tires. They aren't just for rubber tires either. You can purchase them with a pipe fitting on one end. I actually have one out in the garage...

Not all yamabond is created equal!

Yamabond #4 is RTV silicone, yamabond #5 is anaerobic sealant (kinda like K&W copper seal)

I use #5 for case seals as it won't clog up anything after you start the quad. What isn't trapped between the aluminum flakes off harmlessly and will come out the tailpipe. In oil and coolant uncured #5 just dissolves.

 

[Whitty21]

schrader valve is the technical name for the valve system used on tires. They aren't just for rubber tires either. You can purchase them with a pipe fitting on one end. I actually have one out in the garage...

Not all yamabond is created equal!

Yamabond #4 is RTV silicone, yamabond #5 is anaerobic sealant (kinda like K&W copper seal)

I use #5 for case seals as it won't clog up anything after you start the quad. What isn't trapped between the aluminum flakes off harmlessly and will come out the tailpipe. In oil and coolant uncured #5 just dissolves.

thanks for going into detail about the shrader valve, differentiating between yamabonds, thanks man!

 

[sicivicdude]

no problem *coughgreencough*

Seriously though, some sealant on the reed cage (in addition to a gasket back there) will virtually ensure that you will not have a leak there. At least that's fairly easy to take off if you do find out you have a leak there.

For the cases, you have to use the right stuff to begin with... yamabond #4 is an excellent choice as well as a few other types of sealants. I used yamabond #5 on my case halves after lapping each flat and then checking clearances together to make sure they were true to each other. I like using yamabond #5 between case halves because it doesn't get into coolant passages or (worse on 4 strokes) oil passages and block things up. It requires a little extra attention to ensure that the cases will mate perfectly but it's worth it to me.