Compression Test

[Shaka]

I just finally went and picked up a compression tester and had to try it out!  My ZX50 has been taking up to 6 kicks in the mornings to get it started so I wanted to check it.  The good news is I have a max pressure of about 115psi compression!  Yay!!!  I'm sure there is some wear to the rings, but still good!  It was nice because I could see why it probably takes a couple kicks to get it going.  The first kick produced about 60psi building to the max 115psi after 3-4 kicks.  According to the instructions for the tester this is pretty normal though.  It says to turn the motor over at least 8 times to get the max pressure.  Anyways, I'm a little excited about my new tool and that my scooter has good compression!

[wordslinger]

...now i want one...dammit shaka 

[Shaka]

Harbor Freight, it's not on their website, but item# 66216, $20!  Even comes with a nice case and lots of adapters!

[wordslinger]

Harbor Freight, it's not on their website, but item# 66216, $20!  Even comes with a nice case and lots of adapters!

..pic pleeease...

 

[zombie]

For a compression test I remove the shroud, and use a cordless drill to turn the engine over. (due to no electric start) 120 psi is new out of the box reading so 115 is excellent. Fresh rings will have you right back upm there. 100 or less will get you into the no start zone. Did you price the Snap On tester? $240.00

[zombie]

http://buy1.snapon.com/catalog/tools.asp?tool=all&Group_ID=1424&store=snapon-store

[Shaka]

Dang that Snap on one is ridiculously priced!  I just plugged it in and hit the kickstart.  I did have to take the cooling shroud off to get the adapter out of the head though!  I tired doing the test without removing anything, but I couldn't get enough grip on the adapter to get it loose.  I think the o-ring was sticking.  I don't know how much fresh rings will help because I know there is a chip in the Niksal plating near the bottom from when I first installed the cylinder kit.  I had the oil line hooked up wrong!  I'm lucky that's all that happened!  I would have hated to ruin a brand new cylinder before I even got to ride it!  I'm just happy the compression hasn't really dropped since I installed it!  I had it tested after install and I believe it was 120psi.  Here's a pic of the kit!

[sidthesloth]

Hey shaka, that looks like a good score for $20, I will have to see if I can find something like that so I can test before removing the old cylinder. My starting problems are rather unusual in that when it won't start on the starter motor it will usually go on the first or second kick, though not always. Zombie, you said no electric start, did you take it off or did your scoot not have one?

[Shaka]

Hey Sid,  Before I installed my cylinder kit I had the same starting issues.  It wouldn't start with the electric starter, but would with the kick.  I have attributed it to low compression as I had minor scoring in my stock cylinder.  Also, it seems these ZX's may have weak starters to begin with!  Since installing the new cylinder my electric starter is too weak to turn the engine fast enough to start.  I don't know if it is because of the higher compression, or my starter has been getting weaker from the get-go.  I don't even try to use my electric start anymore!  I still have it, but don't even try anymore.  My scoot takes anywhere from 3-6 kicks to start in the morning, and first time every time after.  It seems it was taking 2-3 kicks in the morning to start, but now 3-6.  I'm guessing the colder weather has played a part also!  I got the compression just to verify that I wasn't needing to start saving for a new cylinder, but it appears I'm still within spec.!

[zombie]

I fixed mine twice within 3-4 months. (new relay-new brushes) figured it was more of a "cosmetic selling point" and just removed it, and the jack shaft.

[sidthesloth]

Hey Shaka, it seems that it may be that way with mine, I want to do a compression test before I strip it so I know what I have got if I ever want to use it again, ( I am a curious person anyway). I love the look of the kit you got. The starter on mine spins over ok, she just don't want to start sometimes, but like you said the higher compression may be a bit much for the starter, when you start increasing bore size you are getting away from the manufacturer's specs so maybe a larger starter is needed, or just kick start as you are doing.

[zombie]

The only way around the lack of starting power is to switch to an F-5 battery. It takes a little modification to install because it is about 3/4" taller. That was the first thing I did when I bought the scoot. Now I don't even use it! Ps. the gell cells are only about $15-20 bucks more. It is a good idea to comp. test before disturbing your set up so that you know where you stand.

[sidthesloth]

G'day Shaka, that compression test kit you bought, is it any good, I have found it on two sites, one wants $30+ postage, the other wants $21+ postage but the one with the cheaper price does have some bad feedback (though some good as well). Your opinion will be appreciated.

[Shaka]

So far I've only used once.  It was very easy to use though!  It appears to be good quality, the finish and machining on the adapters are well done.  It holds the needle at the max pressure so it's easy to read.  It has a button below the gauge to release the pressure when you're done.  I also really like tools that come in a case!  Overall, I'm very pleased with it's performance especially for $20!  There is no way I'd pay $250 for the Snap-on unless I was using it daily for my job, just doesn't make a lot of sense!  I think for the occasional use I will give it, it will work very well!

[sidthesloth]

Thanks for that shaka, @ $21 it is not a lot to lose if it does turn out to be cheap and nasty in the long run. The valve adjuster tool for my GPX was going to cost $93, needless to say I made do with my conventional tools.