Author Topic: Compression ? (Read 7266 times)

Bigred · « **on:** July 26, 2013, 12:45:41 AM »

Ok it's a spacer plate motor new ring and piston and bore and has a cool head with pump gas dome. Did a compression check (yes gauge is good and accurate) it blew 150. Now I have paper gaskets on top and bottom of spacer plate. I have a cr gasket under the cool head it's a 3 piece. Do I undo the 3 piece gasket and use one to bump it up or is there another way. Also I only had the head pipe mounted not the whole exhaust will that make a difference. Thanks or any and all input

Polonda · « **Reply #1 on:** July 26, 2013, 01:00:05 AM »

You need to at least check your squish with some solder. Changing gasket thickness at the base will change port timings some. At the head will not. Both will change your squish. Get a squish measurement for us then we can make some recommendations based of what type of gas you want to run. Best way is to do a UCCR and squish test.

Bigred · « **Reply #2 on:** July 26, 2013, 01:06:40 AM »

Ok got a sticky on how to find the squish? It's a trail rider 93 is all she gets. Just want 180-190 compression

Bigred · « **Reply #3 on:** July 26, 2013, 01:09:41 AM »

Nm I found it

F-Red · « **Reply #4 on:** July 26, 2013, 06:51:46 AM »

Quote from: Bigred;5774

Did a compression check (yes gauge is good and accurate) it blew 150.

Has the motor been broke in? A fresh unfired motor, typically will have 20-30psi less than a broke in motor.

jcs003 · « **Reply #5 on:** July 26, 2013, 07:13:49 AM »

what kind of compression gauge? some adapters dont go as deep as the spark plug and will throw off you readings.

also, as F-Red stated, if the rings arent seated yet the compression will be lower.

john

Bigred · « **Reply #6 on:** July 26, 2013, 09:00:46 AM »

Motor never been fired yet. Not sure if my jetting is even close to have it fire lol. Gauge is a good one my buddie is a mechanic. Says its within 1 psi accuracy . Ill have to get it all buttoned up and try to get it to fire. Do some heat cycles then check it again thanks for the advice

trx88 · « **Reply #7 on:** July 26, 2013, 09:31:01 AM »

Quote from: F-Red;5793

Has the motor been broke in? A fresh unfired motor, typically will have 20-30psi less than a broke in motor.

there were times i wish i had known that..

F-Red · « **Reply #8 on:** July 26, 2013, 09:51:01 AM »

Quote from: trx88;5817

there were times i wish i had known that..

Me also! Some of us are monetarily taught! :greedy_dollars:

F-Red · « **Reply #9 on:** July 26, 2013, 09:53:30 AM »

Quote from: Bigred;5809

Motor never been fired yet. Not sure if my jetting is even close to have it fire lol. Gauge is a good one my buddie is a mechanic. Says its within 1 psi accuracy . Ill have to get it all buttoned up and try to get it to fire. Do some heat cycles then check it again thanks for the advice

Set the jetting rich. Work it from there.

Quote from: trx88;5817

there were times i wish i had known that..

Me also! Some of us are monetarily taught! :greedy_dollars:

Rupp250 · « **Reply #10 on:** July 26, 2013, 09:59:31 AM »

Like stated, measure UCCR and squish. I don't use a compression gauge to tell me how to set up a motor. I use my builder for that.

I do use a compression gauge to monitor engine health. And the one I use is off, but it reads the same consistantly though. If you read the gauge then went to kick it over, you would be like huh?

Bigred · « **Reply #11 on:** July 26, 2013, 10:38:06 AM »

Bought my carb off .net few years ago its setup for a 400 plonda so im sure it will be rich already

Rupp250 · « **Reply #12 on:** July 26, 2013, 10:56:21 AM »

Pull it apart and let us know what jets and needle are in it. Should be able to tell you where to start at.

At the same time it would be good to make sure it is all clean.

Polonda · « **Reply #13 on:** July 26, 2013, 01:23:59 PM »

Big motors can actually use smaller jets sometimes due to the piston having a bigger pull on the jet. Better open it up and check that out like stated above.

Bigred · « **Reply #14 on:** July 26, 2013, 11:30:15 PM »

Ok will get the numbers tomorrow carbs clean went thro it when I got it then went into a plastic bag