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DOHC Rattle?

  • Thread starter Thread starter RevsGS850G
  • Start date Start date
R

RevsGS850G

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New to the forum, new to the GS experience.

I recently acquired a 1981 GS850G, has about 25k miles on it. Rides real good, good take off, nice and peppy, even with my 300lbs on it. The only problem is a bit of what sounds like valve rattle at about 4500 RPM. I noticed on the recent octane thread that higher octane helps with a rattle at about 5k RPM. I just topped off today with reg unleaded and didn't think about the higher octane. I have dealt with auto engines, V8's and such and do know that higher octane will help with pinging, but just didn't think about it with the smaller engines.

Am I headed in the right direction with this, maybe run the tank down and put premium in it. Or do I need to start thinking about a valve adjustment?

I have ridden a few Suki's prior, mostly newer, volusia, katanas, and such, but finances and fuel prices put me back on a bike, be it an older classic. I do like the ride and it feels a whole lot better than the 81 GL1100 Goldwing I had. I just like a lighter bike, and this one feels real good.

Rev
 
I have a 1980 GS850G and She seems to be happiest with 89 Octane. Sometimes I mix 87 or 91 in depending on how She is running and Weather Conditions. These Motors are a bit Noisy but Very Solid and Reliable. Welcome to the GSR, I think you picked a Great Bike! :D
 
Thanks for the welcome. My first wife was from Kentucky (Manchester close to London) and yes your signature line is right. land of fast women, beautiful horses and good bourbon.
 
Well, Like I say, They ain't always in the same Order! :wink:
 
Re: DOHC Rattle?

RevsGS850G said:
Or do I need to start thinking about a valve adjustment?
Rev
Click to expand...

At 25k it would'nt hurt to check and should be checked anyway.
 
See if something is loose on the bike. I had a piece of plastic vibrating on the rear cowl that I though was an engine noise, one of the cam covers was loose and that really made a buzz(then it fell off)

Try it in the garage and have someone take the engine up while listening around the bike for where it is coming from. It is hard to tell when you moving.
 
I thought about something loose, but it does it at about 4500 RPM though any gear irregardless of the speed. I put 2 gallons of racing gas 100 octane in on top of the cheap stuff, now it just does it once the engine is warmed up good.

Rev
 
at thirty K all my valves were stretched enough to need adjustment. Id recommend doing it. its worth it to buy the tool, and if ya can stand to wait order the shims you need from somewhere or see if the dealer will trade you some from their service box. if they have one .

Ive run 87 in my 850 and it doesnt rattle, I typically run 89 octane fuel without ethanol.

Id look and see if you have the beginnings of a vacuum leak somewhere, or a fuel restriction. does it go away if you give it more throttle? does it get worse if you roll out of the throttle? could be some type of lean condition.

also make sure no one put hotter plugs in it, as they can get too hot and help cause preignition.
 
Check eBay.

Sometimes a full set of used shims shows up for around 20 bucks. They are 10 dollars each from the dealer. Once you do the valves you will know what sizes are in there so you can get what you need the next time you do it.
I did not use the tool, a screwdriver ws good enough to depress the spring
 
It eases off a little over 5000 RPM's, but doesn't go away entirely. I do have a new set of NGK plugs I picked up today to go in it. ANd I don't really push a bike past the speed limit and 55 MPH puts it at a little over 4k RPM's so I haven't really stretched it to far over the 5k mark except in 4th gear.

I will check on the tool, if it is a standard feeler gauge, I may have one in my box at work, I have done extensive work on V8's and High performance car and boat engines, but still rather limited to small bore bike engines, I learned a little by tearing down a '78 CB550, and an '82 GL1100 both Hondas, so I have a little bit of a learning experience to go. I am still waiting on my Clymers manual. I got the bike on saturday, got tagged and insured on monday and have put about 300 miles on it. Now it is raining today and the next couple here in NC, I may be able to clear out the carport and get something done to it either tomorrow or Saturday. It just feels so good to be back in teh wind again that it's hard to stop and do a minor tear-down.

I hunted down a knowledgeable forum on the GS, just like I did on my Classic Wing I had. This group seemd to have a wealth of information over several others that I looked at.

Rev
 
there are other GS groups? :P

its the smallest couple feelers on most sets, very tiny clearance on em. I used the depresser tool, makes the job easier, but whatever works for ya.
 
I recommend a carb resync when your done. Tweaking the valves on my 650 threw the carb sync off a lot. I had one that was at .005, almost twice what it should be. I noticed a quieter engine immediately and better mileage, I picked up around 3 to the gallon on average.
 
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