Which Compression Tester to buy ?

[LTGTR]

I am considering buying a compression tester but have read that you may get varying and "low" results if you have one with the valve at the gauge end of the hose instead of at the "connect to the engine" end of the flexible hose. The reason given is that because its a small engine the volume of the flexible hose effects the reading.
I have read lots of posts in this forum about compression testing, but that issue hasn't been mentioned.
Geoffxs (equivalent of Mikesxs here in Australia) sells one that seems reasonably priced but has a longish flexible hose in the kit and looks the same as the one Mikesxs sells.
Has anybody had experience with different testers including the one Mikesxs and Geoffxs sell and can advise on the correct one to buy please.
Kind Regards - Ray.

 

[jetmechmarty]

I bought one with the relief valve at the gauge. I bought it 25-30 years ago at my local Carquest auto parts store. It's been used quite a bit over the years and it appears to be functioning fine, still. I like the kind that screw in and seal with an o'ring. Get one with several adapters. I would recommend going to an auto parts store where shops buy their parts. They will have what you need.

 

[willis]

This is the one I bought on Amazon for $20. No complaints with it. I think the vast majority are made by the same company overseas.

 

[jetmechmarty]

This is the one I bought on Amazon for $20. No complaints with it. I think the vast majority are made by the same company overseas.
View attachment 180950

That kit certainly has all of the adaptors and a very nice box to keep it all in. The price was right, too!

 

[XSLeo]

The bit of variation you may get from the valve position I don't think is all that concequential. As long as it reads concistantly. The I have one I bought from a parts store that has the valveup by the gauge with about 18 inches of hose and several adapters. It works fine.
If your pressures are even side to side and at least 125 psi your bike will run fine. If the pressure is less than 100 psi then it may be ok. If the bike has sat for very long a thin layer of rust can form on the cylinder walls, rings, valves and valve seats. So when you first revive a bike the pressure may be low but after a few miles this rust gets worn off and compression comes up.
I think most any gauge in the $30 to $50 range will be a good one.
Leo

 

[gggGary]

My gauge is 25 years old similar to the red box gauge above. I replaced the gauge part with a quality unit from a plumbing supply house a decade or so ago but that made little difference in readings Every now and then I remove clean and oil the Schroeder valve if the pressure bleeds down when I stop kicking. I've taken 100s, maybe thousands of readings with it on everything from big block chevs down to chainsaws and weed eaters.

 

[650Skull]

Bought mine years ago and it cost around $60.00, (we are talking Australia here and before internet sales unlike today and store bought). Today it costs $138.00 with a discount of $30.00. Only 3 adapters
https://www.autolinkparts.com.au/pro-kit-4-piece-petrol-engine-compression-tester-k

What i like about it is with the hose and extensions it is easy to read when doing compressions on a bike

 

[gggGary]

with the hose and extensions it is easy to read when doing compressions on a bike

Yup I keep a piece of copper house wire wrapped around the gauge stem and quick wrap it around the clutch or brake lever for easy viewing while kicking or cranking.

 

[bosco659]

I have a set from Mac Tools. Has extra hoses and adaptors for different applications. Fairly costly and I wouldn’t buy something like this if it’s only for the bike. Some of the kits mentioned above look good. When looking at compression numbers, the max psi is important but equally important is the varaiation from one side to the other.

 

[xjwmx]

I got mine at a Goodwill store decades ago. Seems to work fine. I have left the $1 price sticker on it. Last time I used it the hose wanted to blow off, so I need to pull a couple of zip ties around it real tight.

 

[LTGTR]

Thanks for all your help.
I ended up buying a $25 one from Amazon and it works fine.
My results are a little low, but I expected it would be because its a fairly high mileage motor.
127 psi Left Cylinder - 132 psi Right Cylinder.
It starts and runs pretty good so I will just be leaving it alone for the moment.
Regards Ray.

 

[5twins]

Did you test it warm or cold? You should get better readings on a warm motor.

 

[joebgd]

fairly high mileage motor.

What is considered high mileage on these guys? Assuming average maintenance was being done.

 

[gggGary]

Assuming average maintenance was being done.

 

[GLJ]

Pessimist=always thinking the worst=Gary!

 

[jetmechmarty]

What is considered high mileage on these guys? Assuming average maintenance was being done.

I just took mine apart with 57,000 miles on it. It had never before been apart. It needs the attention.

 

[gggGary]

Time as well as miles is a cruel mistress.
but for "not abused" street bikes with at least occasional oil changes, low to mid 30K miles is prolly getting to due time for a top.

 

[gggGary]

I just took mine apart with 57,000 miles on it. It had never before been apart. It needs the attention?

Marty's bike was still good to go!

I'll vouch for him.

 

[LTGTR]

Thanks for the replies.
The test was done hot - both plugs removed - strong battery - only about 4 cranks/cycles of the starter motor (say 5-6 seconds) - reading increased with each crank then stopped - throttle wide open.
Just after I bought it the head gasket had to be replaced.
The bike was imported from USA with 41,000 miles - I've only done about 200 miles since owning it - maintenance record completely unknown - it doesnt appear to have ever been worked on (other than replacing the head gasket mentioned above) - completely original condition (never been fuc.... around with).
Regards Ray.

 

[5twins]

I'm sure you could keep running it but a topend freshening up certainly wouldn't hurt anything. I'd start planning for it, maybe in a season or two. Start shopping around now and you may be able to find good deals on some of the parts you'll need. Something to keep in mind is most all of these need that pesky front cam chain guide replaced because they're routinely failing due to their age. That's mainly why mine came apart but while in there I also replaced the rings, valve guide seals, and the cam chain. I'm surprised you didn't look into doing some of that stuff when you replaced the head gasket.