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Message started by Jsud04 on 02/05/14 at 06:58:51

Title: decompression adjustment
Post by Jsud04 on 02/05/14 at 06:58:51

Hello all,

1. The adjustment is made at the solenoid by pushing the shaft out with a finger from the frame side of the decomp...correct?

2. Do I need to have both valve covers off or can I just set the notch to TDC and not worry about intake?

3. What are the consequences of a mal adjusted decomp. I.e. can it be mal adjusted and still run?

Ummmm let's see....

I'll throw in a, what's the meaning of life?

Title: Re: decompression adjustment
Post by Tempted on 02/05/14 at 09:31:34

Its adjustable at the bracket attached with two screws to the valve cover. Adjust the top nut to remove slack from the line, then raise the bottom to hold it there. If you have way too much tension then you could possibly have an issue with it hanging but it would take a lot. My Savage starts nicely without the D/C solenoid hooked up.

Title: Re: decompression adjustment
Post by Dave on 02/05/14 at 09:44:05

I don't believe the decompression solenoid really needs adjustments once it is set at the factory. It is important that the lever arm be able to return to the "off" position completely, and there should be enough slack in the cable to allow the lever to return to the "off" position. In this position the decompression cam inside the head is not in contact with the rocker arm. If the cable is overly tight and pulls the decompression lever up too much - you will either get a tapping sound when the valves return to the closed position.....or worse case is that it is so tight that it does not allow the exhaust valves to close completely.

Yes, in most cases the engine will start with the decompression solenoid taken off or disfunctional - however cold temperatures, thick oil, or a weak battery can affect how well the engine can turn over on that first compession stroke. The potential problem is that when you turn the engine off it could stop rotating with the piston part way up on the compression stroke....and the next time you hit the start button the electric starter will not only have to overcome the inertia of the non rotating crankshaft and piston - it also will have to overcome the compression in the cylinder without any momentum.....and that is hard on the starter. Suzuki designed this bike to be operational at all temperatures and tried to make it reliable.....so they installed the compression release to make it easier for the starter to get the engine spinning on that first engine rotation when it could possibly be on the compression stroke. I have the decompression solenoid removed on my bike as the GT550 tank did not allow room for the decompression solenoid. I have a Wiseco piston installed......and about 1 out of every 100 tries the starter could not push the piston up on the compression stroke and I had to let up on the starter button and move the bike in gear to rotate the engine past TDC. This winter I installed a handlebar mounted lever to operate the decompression feature when I need it.

Title: Re: decompression adjustment
Post by Jsud04 on 02/05/14 at 09:45:30

..(Hummmmmm) interesting.

Title: Re: decompression adjustment
Post by cafecarl on 02/05/14 at 19:21:57

Dave, how about a pic on that bar mounted c/r? Sounds classic.
Last summer I had a car in front of me stop short as we were leaving a green light. I grabbed the brake no problem but stalled the bike. That's when "Murphy's law of piston position" insures that the it will be in the wrong spot for a quick restart.

Title: Re: decompression adjustment
Post by Art Webb on 02/06/14 at 00:55:17

0D363B2C3D312A2C373F322D5E0 wrote:

This winter I installed a handlebar mounted lever to operate the decompression feature when I need it.

both my GN 400s had this, stock. I prefer it to an electric one

Title: Re: decompression adjustment
Post by Dave on 02/06/14 at 05:05:03

I switched my bars over to 7/8" bars, and I used a BMX bicycle brake lever. It may be possible to bore the mount to 1".
http://i60.tinypic.com/hwfg3m.jpg

I had to make a longer lever to go with the longer movement of the brake cable, and a new mount for the cable that lined up with the longer lever.

http://i57.tinypic.com/2zsa2qr.jpg
http://i58.tinypic.com/30jqulf.jpg

Title: Re: decompression adjustment
Post by verslagen1 on 02/06/14 at 09:44:11

I adjust by ear and function.
Adjust as loose as possible to function.
The savage can start on the 1st rev.
But adjust it too loose and the starter can stall.

The decomp activates for a little under half second.
The starter turns the engine at about 300 rpm or 5 revs per second.
So half second is about 2 revs.

So the way I adjust it, only the peak compression is released and it is enough to prevent the starter from stalling but enough compression to start the engine.

Note: All my engines have the starter torque limiter. And I don't have problems starting, so I don't have prolonged starter usage.

Title: Re: decompression adjustment
Post by Serowbot on 02/06/14 at 10:38:19

Yup,.. the manual calls for some spec measurement at the solenoid, but that's kinda' dumb... because you adjust at the lever...
I just make sure there is some slack on the cable when the sol ain't engaged...