What compression tester is best?

[250X_project]

Is it okay to use the rubber cone testers, or would they leak and be inacuarate?

[stocktires]

I wish I knew, I'd have one

[bradley300]

i need one also, so i hope someone answers. i found one at sears, it goes to 300 psi and was only 40 bucks. but i didnt know if it was good enuff

[Colby@C&DRacing]

Over the years I have use many comp testers. I haven't had very good luck with the rubber cone ones. I have used the craftsman one and it works just fine and is available at any sears.

[bradley300]

is 300 psi enuff for a hi-comp 450? i have no idea what kind of numbers they put out, but my blaster was 175psi. i probably wont ever go more than 12:1, so should 300psi be enuff?

[Colby@C&DRacing]

300 psi will be more than plenty

[vze2hnvz]

Believe it or not, this one actually worked well for me :


http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92697


The system is simple enough, the guage's calibration is the most important part of the tool. Mine was very close when tested against another top brand tester.

[bwamos]

Where did you get an adapter for that?

Most ATV plugs are 12mm. That kit only comes with 14mm & 18mm adapters.

I've seen people take an old spark plug, core it and thread it to make an adapter, but that would be a royal pain in the butt since the spark plug material is usually very hard....

[GPracer2500]

When I went looking for a 12mm adapter it wasn't much cheaper than buying a cheap guage that included the adapter.

I bought a tester from Walmart and it included a 12mm adapter. I tested it against two other guages and all three read the same--so unless all three of the guages are identically inaccurate (seems unlikely) the Walmart guage is resonably accurate.

I've had a number of guages over the years and it seems where the cheap guages let you down is not in the initial accuracy, but how well they maintain that accuracy after getting kocked around a bit. I've got a couple old (cheap) gauges and they all measure differently--the one I recently threw away wouldn't even hold a reading anymore.

[86 Quad R]

i use the guage similar to the one sears sells and it came with the 12mm adapter. what i do to get the other adapers, is to use an old spark plug for that particular engine, break the porcelin off and grind the taper where the porcelin meets the plug. once the taper is ground off, the core comes out and you are ready to JB weld a 12mm non-fouler into the core. works great for those lil bitty 10mm honda 110's and 200's ect ect.

[250X_project]

Wow that's a great idea, I actually am after a 10mm, also would like one to fit my X- must be a 12..I haven't checked. Now I just need to find a small enough non-fouler. I could only find 14mm.... THANKS A LOT GUYS!!

[2muchquad]

check your inbox 250x:chinese:

[86 Quad R]

Originally posted by 86 Quad R
i use the guage similar to the one sears sells and it came with the 12mm adapter. what i do to get the other adapers, is to use an old spark plug for that particular engine, break the porcelin off and grind the taper where the porcelin meets the plug. once the taper is ground off, the core comes out and you are ready to JB weld a 12mm non-fouler into the core. works great for those lil bitty 10mm honda 110's and 200's ect ect.

250X_project i realised later that i was wrong about my fitting sizes(blonde moment?)
:D the size that came with my tester is 14mm and the home made one using the old plug is a 12mm.

[DieselBoy]

i got the one from walmart also, and it works great.

[sandshots]

so what kind of pressure are we expecting these bikes to put out?

400ex?
450r ?

i have one of each and want to test them. the 400ex is an 02 and probably ready for a piston.

[250X_project]

2muchquad- Check my inbox???? You need to clean yours! :D I've tried to reply twice now including about 5 mins ago :rolleyes: Just get back to me when you clean it. ;)


86 Quad R- That's okay. I greatly appriciate you letting me know that. I could still use a 12mm as well so.. still a good idea. Thanks you!
:D

[DieselBoy]

Originally posted by sandshots
so what kind of pressure are we expecting these bikes to put out?

400ex?
450r ?

i have one of each and want to test them. the 400ex is an 02 and probably ready for a piston.

Don't remember the exact specs in the book, but I believe stock it's supposed to produce 100-125 PSI. on a stock piston.

don't know what to tell ya on the 450r

[250X_project]

100-125 seems pretty low, as the 250X/300EX is 170-199PSI. Static being- 8.9:1 / 9.4:1.

[DieselBoy]

I realize they're low, and I had to take a second look to be sure it was for real. It is infact 100-125 believe it or not.

[250X_project]

No kidding. Those numbers are from a manual? :eek2:

[GPracer2500]

The reason they are so low is because of the auto-decompression mechanism. The mechanism doesn't disengage until 600rpm (or something like that) which is above the cranking speed. A 400EX with the auto-decomp removed pumps higher than the 125psi spec.

A stock 04/05 450r specs at 108psi--again because of an auto-decomp mechanism. The stickler with the 450r is that even aftermarket cams utilize the auto-decomp.

[250X_project]

Alright now I understand, Thanks!