Just be careful. The whole point to the DC is to take the strain off of the starter and start easier. Don't crank it any longer than needed with the DC off.

sundance wrote:
I did not disconnect the decompression solenoid. Where is it and what is the proceedure? that sounds like something that would cause this issue.

It is impossible to get correct readings with the decomp sol working. The whole purpose of the solenoid is to lower the compression so that the bike starts.

Doc

Has anyone read the compression test in the clymers manual. It states to remove all 4 plugs and insert them into their spark plug caps. Then connect the compression tester to one cylinder and so on and so forth. I'm pretty sure your gonna get pretty close to 0 on both cylinders like that. Instructions: FAIL. The rest of the instructions just say to hold the throttle wide open and crank. Given that these bikes have a tps, I'd say wot shuts off the decompression solenoid.

I see in the clymer manual where the decomopression solenoid is and also where the wires for the selenoid go, up near the fuse box. I guess the question is, do you need to take the solenoid off, or just disconnect the connecters by the fuse box?

Sundance

vwtech0 wrote:
Has anyone read the compression test in the clymers manual. It states to remove all 4 plugs and insert them into their spark plug caps. Then connect the compression tester to one cylinder and so on and so forth. I'm pretty sure your gonna get pretty close to 0 on both cylinders like that. Instructions: FAIL. The rest of the instructions just say to hold the throttle wide open and crank. Given that these bikes have a tps, I'd say wot shuts off the decompression solenoid.

I know this post is old but I had this same question about the clymers manual incorrect compression test instructions. Would the correct instructions be:

1 - disconnect all spark plug wires,
2 - remove one plug from each cylinder (or do you remove the plug from one cylinder at a time),
3 - attach the compression gauge to the first cylinder,
4 - fully open the throttle,
5 - crank the engine,
6 - repeat for the second cylinder.

Is it correct that WOT shuts off the decompression solenoid?

Thanks in advance.

dave

====OLD THREAD!! CREATED NEW THREAD WITH SAME QUESTION. SORRY FOR ANY CONFUSION!!====

sundance wrote:
I have a midnight star 2004 1700 with 60000 mi. I just adjusted the valves and while doing so bought a compression tester from auto zone and checked the compression. I'm not sure how accurate the tester is. With the engine hot psi is 120 in the front cylinder and 118 in the rear. The standard is 175 and minimium is 145 psi. I am not burning any oil and have no compalint with the performance of the motorcycle. Since this is quite a bit below specs I'm not sure what the next step should be?
I have thought about replacing the rings this winter and have looked at the test articles for tearing down the top end of the engine, I don't see that to be a problem for me. I have also thought about installing high compression pistons while I have the engine apart. If I do this is it necessary to replace the ignition system or have any thing done to the valves?
I guess to sum it up with two qustions:
How concerned should I be about the low psi?
If I go with high compression pistons what all else should be done?

Sundance
=======================

Well did you remember to open the throttle to ensure throttle plate is open fully when doing compression test,slide needs to be held open too?

If not the throtle plate will be closed greatly reducing amounhjt of air avail to be sucked into cyls & compressed that in most cases will reduce compression reading.

But you only had a 2 psi dif between front/rear cyls which is good.

Try doing an 2nd comp test like this.

* Fully charge battery.

* Remove 1 plug from front cyl and both rear plugs to reduce load on starter to better spin motor over.

* Now do comp test on front cyl with throttle wide open & slide held open too for approx 5-6 seconds or so.

* Then remove 2nd plug from front cyl so now both plugs are out from front cyl so motor spins over better for comp test of rear cyl and install 1 plug in rear cyl.

* Now do comp test on the rear cyl for the same approx 5-6 seconds with throttle wide open & slide held open too.

Doing the comp test as i suggest above will yld best/most consistant results esp if you didnt have throttle wide open to ensure throttle plate is fully open so motor could suck in proper amount of air for best/highest compression reading.

Scott

Disregard comment, an old post.

USAFRETIRED wrote:
Disregard comment, an old post.
=================

LOL!!!!!

Ah crap!!

You got me!!

Scott

sundance wrote:
I have a midnight star 2004 1700 with 60000 mi. I just adjusted the valves and while doing so bought a compression tester from auto zone and checked the compression. I'm not sure how accurate the tester is. With the engine hot psi is 120 in the front cylinder and 118 in the rear. The standard is 175 and minimium is 145 psi. I am not burning any oil and have no compalint with the performance of the motorcycle. Since this is quite a bit below specs I'm not sure what the next step should be?
I have thought about replacing the rings this winter and have looked at the test articles for tearing down the top end of the engine, I don't see that to be a problem for me. I have also thought about installing high compression pistons while I have the engine apart. If I do this is it necessary to replace the ignition system or have any thing done to the valves?
I guess to sum it up with two qustions:
How concerned should I be about the low psi?
If I go with high compression pistons what all else should be done?

Sundance

Make sure decomp solenoid is disengaged as that will give you very wrong results.

Manual says to remove all spark plug wires and ground them. Remove the spark plug one from front and one from rear. Install gauge open throttle full and crank the engine until the reading stabilizes. The difference between cylinders shouldn't be over 14 lbs. Compression at sea level: Minimum = 142 psi Standard = 171 psi Maximum = 199 psi.