1980 GS450 L 40k miles sputtering Help!

[GSe-James]

Hello to all the GS people. Glad I found you!
I have 450 with 40,000 miles.
Last week she started sputtering @ cruzing speeds.
I cleaned out the tank and it got a little worse.
I dipped the carbs and ordered new o-rings, one was broken on adjustment screw.
Prior to taking carbs off I tested compression with a gauge and got 95 on each side, seems very low to me ??? Anyone know what the acceptable range is for a 450?
I am not sure of the test procedure to use but I did get the same reading last summer when the bike still ran fine.
The bike starts right up, idles nice, no smoke...
She has been a nice commuter for past three years.
Hoping to get a little more out of her...
Thanks in advance for any help.

[tkent02]

It's all in here somewhere:

http://members.dslextreme.com/users/bikecliff/

Start reading.

[tom203]

While you're busy reading, reflect on what maintenance you've done and give us some clues.
How did you clean out tank? did you remove and attempt to clean petcock?

[Tamara]

Have you also checked for vacuum leaks? 30 year old boots on either side of the carbs could be cracked and leaking.

[pete]

I think 150 is good for compression off the top of my head, but check the manuals to be sure.

How are you compression testing? Throttle at WOT while you crank the bike?

[GSe-James]

Update

Thanks to all for the help.
I can not download the 80 meg Clymer manual with my dial up connection, so I ordered a Clymer manual off ebay. When I get it I will try the valves and timinng.
I did the carb dip and new o-ring procedure last week but still sputtering.
Battery has lasted three years but it is taking a 17 volt charge !
I suspect the voltage regulator is blown or wired wrong.
Could this cause poor performance / missing and sputtering?
I found no vacume or air leaks. Rubber carb boots are soft with no cracks.
Compression was tested cold with open throttle @ 92 psi
Oil has always looked like honey and I change it with filter every 3k.
I cleaned out tank by removing and rinsing with clean GAS and additive.
Did not clean out petcock as it seemed to flow good, but I will check that.
Back with more when I know more... James

[Sci85]

I would also check the coils and plug wires. I have had plug wires that had worn out creating a miss that feels like sputtering. Pretty easy to check too.

The Haynes and probably Basscliff's site will have the coil testing procedure.

Good luck.

[tkent02]

The valves are likely your problem if they haven't been adjusted lately. Do not use the Haynes procedure, it is wrong. Use the Suzuki procedure. You will find it in Cliff's page.

[Sci85]

If the valve clearance is off, it would have developed the sputter over time, not suddenly, and wouldn't affect just cruising speeds. It's always good to check but they are not your issue. It's either fuel or ignition related. Start with the easiest, most obvious things then work you way to the more complex, harder tests, performing or changing only one thing at a time and keep a log of what you did and the changes you made at each step. Post them up as you go along and we can comment on them.

Oh, and dipping the carbs is just part of cleaning them. You need to blow out the passages with compressed air and remove all the jets then use a piano wire to poke all the little holes in the jets clear. However, like valves, carbs just don't suddenly become dirty one day. It happens over time and so do the symptoms. So I would suspect bad gas, dirty gas, or electrical issue.

Good luck and let us know how it works out.

And are you sure it's a sputter (cutting out) and not surging (speeding up and down)?

[GSe-James]

No book and a slow connection

This all started about a month ago.
I was riding to work everyday about 10 miles each way and I noticed a slight sputter at about 45mph.
Over time it got worse. Now the bike is basically unridable.
She craps out at around 35.
There is some surging but mostly seems to be cutting out.
She goes OK in 1st and 2nd gear.
I dipped & cleaned the carbs according to the gs-450 pdf on bike cliff.
I used guitar string to clean holes and compressor / carb cleaner...
I only have dial up connection and most of the pdf files on bike cliff will not download for me... tried all morning to get the valve adjusting pdf.
I get about 10% and the download quits with no error messages.
Will the Clymer book have the correct valve proceedure?
Could the regulater be causing the trouble or fry the cdi ignitor box?
I have a 12 volt battery with 17 volts !
The valves have never been adjusted since I got the bike 14 years ago.
I have put 10,000 miles on it in last three summers. Prior to that is was stored indoors for a very long time...

[Sci85]

How are you getting 17V to the battery? What procedure did you use?

If the valves have never been adjusted then yes, that needs to get done immediately. Go to the library and use thier computers to download the necessary pdf's.

Sounds like the carbs were done properly. Did you replace the orings on the carb boots?

Again, develop a plan starting with easiest and progressing to more complex. Follow the plan and document each step along the way. Post results.

Let's start with the valve adjustment then carb orings if not done already. Then move on to coils, plug wires, R/R, etc.

[GSe-James]

17 volts?

Voltage regulator must be bad ... I think it has been for a long time.
I will adjust valves now...
I have Clymer manual in hand and a Haines manual at the library.
This bike is a sweet little jewell and I will find a way to fix her.
Perhaps a ring job this winter.
Is the valve adjustment in the Clymer manual correct ???

Thanks, James

[Sci85]

I don't know if the Clymer manual is correct or not as I don't have one. I use the suzuki factory service manual. Look around, you should be able to find one on the 'net. Or Cliff's site probably has it.

And I recommend you fix that R/R asap before you destroy your battery and who knows what else.

Oh, and it will help to put where you are located in your info. Someone from the forums may be close enough to lend a hand.

[GSe-James]

Valves tight

I pulled off the valve cover and checked the play 3 ways.
1 with the cam, lobes perpendicular to head surface,
2 with lobes perp. to tappet.
3 with both cam end marks pointed @ each other.
Seems to be a few opinions on where the lobes should be.
Broke the gasket so I ordered another.
The readings are too tight for my .04 mm gauge. Ordered a .03mm set
Wondering if the tappets pump up and cause tight reading?
Could this cause my low compression reading? If the valves have no play they might not seat properly...
My digital voltometer was wrong!
My voltage is correct @ 14+ with analog meter.

[pete]

To check valve clearance, the lobes need to be perpendicular or parallel to the valve cover gasket surface.

Make sure when checking one that the lobe on the other end of the same cam is not pushing down on the bucket. I've noticed that tends to give you an incorrect (smaller) reading.

A tip I was given is that if you can't measure the clearance (too small), try rotating the bucket. If the bucket rotates, you at least have some clearance and one size smaller shim will probably do. If the bucket does not rotate, you have absolutely no clearance and will likely need to go down at least two shim sizes.

Having no or little clearance can definitely give poor compression figures if it causes one or more valves not to seat correctly.