Pressure/vacuum testing

[DocBob]

I've been lurking here for a while, this is my first post. I want to pressure test a carb and the engine. Has anyone ever made the piece to mount over the intake in place of the carb to hook up a pressure tester? What can I use as a nipple to attach the pressure/vacuum line? I hate to admit it, but the saw I'm trying to fix is an 019. I tried the stihl dealer with the part # for the piece, but they couldn't find it on a list to order one.

Thanks for the help in advance.

Bob

My saws:
026
044
066
KM85 with pole saw
Super 797 (just arrived)

 

[Kneejerk Bombas]

If you only had some access to a blood pressure testing unit...

 

[Lakeside53]

The part number for the carb adapter is 1128 850 4200. You could just use a piece of 1/8 plate steel (or aluminum), two holes to match the carb bolts and a 1/8th hose to 1/8 IP thread into the base material to put your vac/pressure hose onto. Use a piece of rubber between the muffler and cylinder to seal the exhaust.

19T.,. hmmm incredibly difficult to work on... everything had to be done in just the right order or you can't get there from here.. Get a service manual....

 

[DocBob]

Thanks. I considered using a BP manometer, but there is a problem with that. A BP manometer is scaled in mmHg rather than PSI. To pressure test a crankcase, you have to generate about 8-8.5 psi. That translates into about 450 mmHg. The scale on a handheld BP manometer only goes up to 300 mmHg. The bulb/pump can be used to generate test pressure, but you'd need a different guage. It would be ok for pressure testing a carb, though.

Thanks Lakeside, your suggestion is more what I had in mind in my question. I was trying to figure out what material to use for the plate and how to attach the nipple. I was going to epoxy or braze a metal nipple onto a plate, but screwing one in and sealing it is probably better. The part # you gave is the same one I gave to the stihl dealer (actually 2 of them) and neither could find it. Maybe it is not supplied anymore? I have a service manual, it has been a big help. It was on a link I found on this site.

Thanks again for your help.
Bob

 

[Lakeside53]

I think your dealers are messing with you. It is available and costs them $7.80each... It's the most used part from the test kit...

 

[Mack]

That pn is good, but Lake's price is a bit low. Retail is about $20.

 

[Lakeside53]

That pn is good, but Lake's price is a bit low. Retail is about $20.

Shows on the current list at $7.80, but tool are "NET" 'cos they aren't really intended for sale. Stihl even charges the dealer sales tax on such items. Like any item, what the dealer charges you is up to the dealer, not Stihl.

 

[Mack]

Lake, we better check our price files. I just ran the number on the Stihl dealers e-sales site as if I was going to order it, and it came up as 20.50 retail less my discount. Not as a net item. Maybe Northeast is different than your distributor. I know discounts can vary, but I would hope msrp would be the same!
Have a Merry Christmas!
Mack

 

[Lakeside53]

Lake, we better check our price files. I just ran the number on the Stihl dealers e-sales site as if I was going to order it, and it came up as 20.50 retail less my discount. Not as a net item. Maybe Northeast is different than your distributor. I know discounts can vary, but I would hope msrp would be the same!
Have a Merry Christmas!
Mack

Very interesting... PM me (or me you) and we'll figure it out. Mine's on Stihl NW. Ill try it again. It's not like they don't have errors in the system. Media Cat report that the new small WINGED plugs that go into the MS361 muffler are $16.15 each!!!

 

[Mack]

plugs, pn 1135 145 9001 - $1.75 msrp here.
$16.15 would make for a nice margin as they cost about a buck forty. I think there may be few glitches in the price files. I know the electronic files they send me and the prices on the e-sales site don't always match up, but they are usually at least close.

 

[Drive_1305]

I saw in a dirt bike mag once they built a leakdown tester using a threaded type tire valve. They attached it to a aluminum plate they made, then bolted it to the intake, blocked off the exhaust and then pumped it up with a bicycle pump. I think they had a gage on the exhaust plate. A better way might be to build a gage and vavle device that screws in to the spark plug hole. Do a search for 2 stroke leak down testers- there's some that's been made for about $20.00. Then again you might find something cheap at auto zone and adapt it. A saw manual I have says use about 7psi. I read once too much preasure and you can pop out the crank seals.

Here's another idea that looks cheap http://www.off-road.com/atv/ptester.htm I built one similar to this for my dirt bike but never got the exhaust blocked off good. I'll try again someday.

 

[DocBob]

Thanks!!

 

[kf_tree]

doc

here's a simple idea......make your plate, then drill a hole through the plate and put a nut and bolt through the plate with a rubber washer or silicone to seal the bolt. then put it in a drill press and drill a small hole right through the bolt. then slip your hose over the bolt.

 

[stihltech]

tester

Careful with the bolt idea. Cut off the threaded part as the threads will leak, just like a fuel tank vent, the GOOD kind.
If you can drill and tap, a small hose barb would be a good choice.

 

[BIG JAKE]

Very interesting... PM me (or me you) and we'll figure it out. Mine's on Stihl NW. Ill try it again. It's not like they don't have errors in the system. Media Cat report that the new small WINGED plugs that go into the MS361 muffler are $16.15 each!!!

Andy if I pump up a crankcase to 7-8psi what length of time and rate of drop is within acceptable limits on the leakback if any? Also heard negative pressure test should be done do you agree with that or is the positive effective to consider seals good in both directions? 7-8 psi doesn't seem like alot and on the surface(not having done this) I'd say if it's good that way then negative would be good too. Having said that, while the saw is running and on the upstroke may apply much higher neg vacuum in the case but I don't know how you'd quantify that. What do you look for when you are judging crank main bearings also? How much endplay and slop if any is acceptable on an 066? Ideally I'd want none perceptible but things do wear.

 

[Lakeside53]

Andy if I pump up a crankcase to 7-8psi what length of time and rate of drop is within acceptable limits on the leakback if any? Also heard negative pressure test should be done do you agree with that or is the positive effective to consider seals good in both directions? 7-8 psi doesn't seem like alot and on the surface(not having done this) I'd say if it's good that way then negative would be good too. Having said that, while the saw is running and on the upstroke may apply much higher neg vacuum in the case but I don't know how you'd quantify that. What do you look for when you are judging crank main bearings also? How much endplay and slop if any is acceptable on an 066? Ideally I'd want none perceptible but things do wear.

The "spec" says something like 20 seconds to half pressure - it's in the service manual. I find a good saw will hold pressure or vac indefinitely. Not true about positive and negative pressure. MANY saws pass pressure easily, but not vacuum. Crank seals tend to fail under vac, not pressure.

Bearings on an 066 - ZERO perceptible play.... These are deep groove bearings and should exhibit no detectable movement either in end-play or lateral. If they show movement, they are going to fail really quickly, and in any case, the crank seals will quickly fail due to the eccentricity.

 

[BIG JAKE]

The "spec" says something like 20 seconds to half pressure - it's in the service manual. I find a good saw will hold pressure or vac indefinitely. Not true about positive and negative pressure. MANY saws pass pressure easily, but not vacuum. Crank seals tend to fail under vac, not pressure.

Bearings on an 066 - ZERO perceptible play.... These are deep groove bearings and should exhibit no detectable movement either in end-play or lateral. If they show movement, they are going to fail really quickly, and in any case, the crank seals will quickly fail due to the eccentricity.

Ok I'm good on the bearings. I'll have to make some covers to seal the case and I have guages. Positive pressure no problem but on the negative I'm not sure quite how I'll accomplish that yet. What about the compression release-check with and without it installed? If it's good with it in then all must be good right? If not I'll plug it. Some might say take it in but I've got a thing about folks I don't know working on anything-had too many things not done right or screwed up. If I'm cutting into trade secrets with anyone no problem. When I was 12 I blew the gears on a yamaha 125. Decided I'd fix it so I could ride sooner. We took it in as a basket case. After that i paid attention. Found I was good at it. Do it for a living now. Best part is I enjoy it. Guess I'm running on-does the half pressure spec apply to the negative test also?

 

[shadetree]

As far as plates go, I just got some old pieces of bicycle inner tube cut to size, and I put them behind the carb, and the exhaust, then tighten them down, I use a homemade leakdown tester, and a mightyvac vac tester, with piston on bdc
and pressure/vacuum test through the spark plug hole.


Shadetree

 

[BIG JAKE]

As far as plates go, I just got some old pieces of bicycle inner tube cut to size, and I put them behind the carb, and the exhaust, then tighten them down, I use a homemade leakdown tester, and a mightyvac vac tester, with piston on bdc
and pressure/vacuum test through the spark plug hole.


Shadetree

Sounds good-Easier than cutting plates. Any rubber relaxation on longer tests? What saw did you test?

 

[Lakeside53]

Ok I'm good on the bearings. I'll have to make some covers to seal the case and I have guages. Positive pressure no problem but on the negative I'm not sure quite how I'll accomplish that yet. What about the compression release-check with and without it installed? If it's good with it in then all must be good right? If not I'll plug it. Some might say take it in but I've got a thing about folks I don't know working on anything-had too many things not done right or screwed up. If I'm cutting into trade secrets with anyone no problem. When I was 12 I blew the gears on a yamaha 125. Decided I'd fix it so I could ride sooner. We took it in as a basket case. After that i paid attention. Found I was good at it. Do it for a living now. Best part is I enjoy it. Guess I'm running on-does the half pressure spec apply to the negative test also?

You need to remove the decomp valve for the vacuum test as it will get pulled open by the vacumm... You can buy the plug from your stihl dealer.

Rubber works well for the exhaust (it's what I use), but the carb is your entry point so an adapter is in order. Easy to make, and fits almost every saw made, so it's worth doing well. If you use the "rubber behind the carb", just use the impulse line for your pressure/vac port.

There are many cheap vacuum devices available at your auto store. Even a bicycle pump (remember those ?) with the washer turned backwards works well.

If you get leaks on pressure, just spray soapy water on the various parts to find the leak. Leaks on vac are harder to find, but as they are almost always seals, I just turn the saw on the side with seal up, and drop 30 wt oil onto the seal. It either "cures" the problem or gets sucked in. When you have a stable vacuum, rotate the crank - sometime a seal with work fine at one spot, but fail at another. The seal under the flywheel is much more prone to failure then the clutch side.