rear adjustable monoshock spring replace - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
 
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post #1 of 8 (permalink) Old 05-16-2018, 07:44 AM Thread Starter
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STEP 1 Disable fuel system. Disconnect the main wire to the coil and spark plug wires; remove spark plugs.
STEP 2 Start the threaded end of the compression gauge in a spark plug hole by hand. STEP 3 Turn the ignition on, depress the throttle, and crank the engine at least four revolutions.

Make sure and post results.

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post #2 of 8 (permalink) Old 05-16-2018, 08:24 AM
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ditto what Les ↑ posted

also since you are checking for worn rings:

step 4: inject about a table spoon of motor oil into the spark plug hole, and do the test again

this is called a wet test. If your rings are worn putting a little oil in there will raise the compression reading on the wet test.
If the oil does not raise the compression then the rings are ok, and if the compression is low for the dry and wet tests then you have a leaky valve seat.

I cannot over state: do not pour more than a table spoon of oil in the spark plug hole. If you try to pour oil in with a funnel from the bottle, you can overfill the compression chamber, hydrolock the piston into the head (space completely filled with oil) and blow out your head gaskets when you crank the engine (or worse). Use a little syringe or one of those little test tube like things that you give medicine to a child with.

BTW, after you do the wet test, the first time you start the bike up it will smoke a lot for a few minutes.
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post #3 of 8 (permalink) Old 05-16-2018, 08:37 AM Thread Starter
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Quote:
Originally Posted by KCW View Post

also since you are checking for worn rings:

step 4: inject about a table spoon of motor oil into the spark plug hole, and do the test again
KCW, good catch and recommendation.

Les B.
2001 Vstar 1100 Classic (sold), Cobra Slash Cut full exhaust, Dropped 1 inch with lowering links, ORK, 4.5 inch handlebar risers, Ultimate passenger seat, Passenger pegs moved forward 4 inches, Handlebar clock, KN air filter, Viking saddlebags, Additional rear lighting
Loose nut "me" behind the bars
2006 Harley Electra Glide Ultra Classic

https://sites.google.com/site/vstar1100kb/home
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post #4 of 8 (permalink) Old 05-16-2018, 08:46 AM
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If your compression is good and the bike is still losing oil there is one other possibility, but its rare.

The oil pump sends oil up to the bearings on the cam shaft on top of the heads. That is where the oil breather tube is on the rear cylinder. If the passage ways in the head are clogged up with carbon or gunk and the oil cannot flow back down to the crankcase, it will puddle up there and get blown out the oil breather tube, and sucked into the carbs from the air box connection.

There is only a very small flow of oil going up there, so when you first start the bike up it would take a while for the puddle to form in the head area, and start blowing the oil out the breather hose.

When we were addressing the problem in the other thread, where the oil was seen coming out the breather hose, I google this and found a few motorcycles that had that problem.

Im not sure how that much gunk could build up inside an engine, like I said its pretty rare, but it does happen. The bike owners had to tear their engines apart to clean the gunk out.
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post #5 of 8 (permalink) Old 05-17-2018, 08:50 PM
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rear adjustable monoshock spring replace

will the adjuster back off enough to remove and install the coil spring or will a spring compressor be needed on the 650 and 1100 monoshocks, i was thinking about installing the heavier spring from pacific coast star. has anyone tried that progressive spring they sell, is it worth the 90.00

dumb bikers don't get to be old bikers
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post #6 of 8 (permalink) Old 05-17-2018, 09:45 PM
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You will need a spring compressor. Don't know about the progressive spring.
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post #7 of 8 (permalink) Old 05-18-2018, 05:47 AM
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it will not back off enough.
I found the progressive spring worth it, would be nicer to get the whole shock with the dampening also upgraded.
I found it harder to get the old shock off, than to compress and put on the new shock.
This was due to the fact the old stock is still at all points, and the progressive gets increasingly stiff, so the small amount you need to compress the progressive one, sits all in that not too hard to compress range.
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post #8 of 8 (permalink) Old 05-18-2018, 04:32 PM
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... would be nicer to get the whole shock with the dampening also upgraded...
I agree. Although OEM springs tend to fatigue and sag regularly on both front and rear suspensions from my experience OEM shocks tend to fall short in the damping department to begin with and get worse quickly with age. If you're thinking about replacing the rear then I personally would go with a complete assembly and not just the spring.
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