Reconditioning GS450

[paulorv]

Hello Everyone,

Recently I took ownership of an abandoned '82 GS450... my room mate moved out of the country and decided to just leave the bike in my garage. With some mechanical experience under my belt, I would like to start reconditioning and riding this wonderful vintage machine. That's when I came across this message board...

First of all, the guy didn't ride it at all since he moved in but would trickle charge the battery and start it up every couple weeks. It started up just fine for me and I took it for a ride around the block. However, the bike has absolutely no acceleration and would often stall, so I am under the impression that some moderate tuning is required. Another thing I noticed is that after a few minutes of idling the right side of the engine got much hotter than the left. I checked the right plug and noticed a pretty heavy carbon deposit (running rich?). The left plug was a bit oxidized but otherwise normal looking. Apart from that, I would notice a audible "clinking" sound (valves?) coming from the engine at about 4500 RPM. How would I go about diagnosing some of these problems?

I should also mention that the bike is pretty much stock except for the air box has been replaced with "pod" filters. Not sure about which brand, though.

Any help is appreciated. Thanks!

[Mekanix]

1 check if its rejeted for pods
2 put the airbox back on if you can
3 while your in the carbs tear them apart completely and dunk the body's
4 check your valve adjustments
5 check the petcock for a leaking vacuume operated diaphragm that allow's gas to get sucked into the right cylinder and making it so rich.

6 Report back here with what you have for main and pilot jet sizes in both carbs.
7 There are replacement O-rings for the entire carbs at Cycleorings.com and don't forget to replace the intake boot O-rings.
8 ok I'm out of ideas, but all of this is necessary without knowing any history of the bike.

[Thumper88]

check for spark

[pete]

Welcome Paul! The guys should have the main stuff under control there but we also need to see pic's

[paulorv]

Hi Mekanix, thanks for the prompt response.

1 check if its rejeted for pods

I had a chance to take off the carb today and noticed it had not been taken apart in the near past. I would bet it was an unfinished project by the previous owner and the carb was not rejetted for the pods.

2 put the airbox back on if you can

I could not find the original airbox in the previous owner's stuff so I think this isn't going to be an option.

3 while your in the carbs tear them apart completely and dunk the body's

I will pick up some Berryman's and dip the carb this weekend. Should also be able to confirm if it's running stock jets or not.

4 check your valve adjustments

I didn't have enough time to remove the cam cover today, so again, this will have to be a weekend project. I'm actually not quite sure what I should be looking for with my valves. Are there any special tools that I'm required to have?

5 check the petcock for a leaking vacuume operated diaphragm that allow's gas to get sucked into the right cylinder and making it so rich.

I assume you mean the vacuum hose going to the carb? I checked it and it's in decent condition, no cracks or fractures as far as I can tell.

6 Report back here with what you have for main and pilot jet sizes in both carbs.

How should these actually be measured for size? I found BikeCliff's carb spec sheet but have no idea how to compare mine. Signs of wear would probably be able to tell if they are original, though.

Assuming I will need to rejet, would a carb sync be necessary as well?

7 There are replacement O-rings for the entire carbs at Cycleorings.com and don't forget to replace the intake boot O-rings.

Bike seems to have new or nearly new intake boots (see pictures) so I will assume o-rings are good too. I'll report back on the condition of o-rings inside the carb once I take it apart.

8 ok I'm out of ideas, but all of this is necessary without knowing any history of the bike.

Again, thanks for all your help.

Pics:

http://imgur.com/GOuK5

http://imgur.com/Fko0s

http://imgur.com/qchbW

[paulorv]

check for spark

Thumper, I checked the plugs and spark is a good solid blue on both sides.

[Mekanix]

I will pick up some Berryman's and dip the carb this weekend. Should also be able to confirm if it's running stock jets or not.


I didn't have enough time to remove the cam cover today, so again, this will have to be a weekend project. I'm actually not quite sure what I should be looking for with my valves. Are there any special tools that I'm required to have?

I assume you mean the vacuum hose going to the carb? I checked it and it's in decent condition, no cracks or fractures as far as I can tell.


How should these actually be measured for size? I found BikeCliff's carb spec sheet but have no idea how to compare mine. Signs of wear would probably be able to tell if they are original, though.

Assuming I will need to rejet, would a carb sync be necessary as well?

Bike seems to have new or nearly new intake boots (see pictures) so I will assume o-rings are good too. I'll report back on the condition of o-rings inside the carb once I take it apart.

http://imgur.com/GOuK5

http://imgur.com/Fko0s

http://imgur.com/qchbW

The jet's will have a number stamped on them, they are usually on the head of the jet for the main and You might have a 115 or 120 main to start off with.

The fact that it won't rev is because its running so lean. You might want to try a Dynojet kit so you have everything right there to jet it properly and tune it or just go to the fuel thread and ask what people are jetting their carb's for with just pods and stock exhaust.

The pilot jet size is written on the body of the jet and should be 45 stock.

It would be a good thing to do a carb synch after you reassemble the carbs.


The vacuum line from the petcock to the carb might be fine but the petcock itself is often a problem.
The way it works is by using suction to open the fuel tap and allow fuel to flow. If the diaphragm is busted then it will allow you to suck gas through that line and straight into the intake.


For the valve you need feeler gauges and that's it. The manual has specefic clearances between the cam and then valve shim's. You can replace the shim's with what ever size is necessary to bring it back to spec. You can buy brand new from Suzuki or talk to the guy's here in the shim club to swap and trade for the shim's you need.


The orings behind the intake boots take a beating with the heat and often get brittle and crack. Its easy to check with the carb's off. It cause a lean condition with an up and down idle when they go bad.

[paulorv]

The jet's will have a number stamped on them, they are usually on the head of the jet for the main and You might have a 115 or 120 main to start off with.

The fact that it won't rev is because its running so lean. You might want to try a Dynojet kit so you have everything right there to jet it properly and tune it or just go to the fuel thread and ask what people are jetting their carb's for with just pods and stock exhaust.

The pilot jet size is written on the body of the jet and should be 45 stock.

It would be a good thing to do a carb synch after you reassemble the carbs.


The vacuum line from the petcock to the carb might be fine but the petcock itself is often a problem.
The way it works is by using suction to open the fuel tap and allow fuel to flow. If the diaphragm is busted then it will allow you to suck gas through that line and straight into the intake.


For the valve you need feeler gauges and that's it. The manual has specefic clearances between the cam and then valve shim's. You can replace the shim's with what ever size is necessary to bring it back to spec. You can buy brand new from Suzuki or talk to the guy's here in the shim club to swap and trade for the shim's you need.


The orings behind the intake boots take a beating with the heat and often get brittle and crack. Its easy to check with the carb's off. It cause a lean condition with an up and down idle when they go bad.

Valve Adjustment:
Ok, I stopped by AutoZone on the way home and picked up some feeler gauges. Took the cam cover off when I got home and started checking for clearance. The intake valves were just within the lower limit (0.03mm) of clearance but for the exhaust valves I couldn't even get the 0.02 gauge between the cam lobe and shim. I read clearances on these bikes tend to get tight with wear. I managed to remove the shims (zip tie method) and noticed they were probably not the originals, as the left and right side had different thicknesses and one of the exhaust shims was put in upside down. I couldn't verify exact thickness since I don't have a caliper, but looks like I'll be needing new ones for all my valves.

Petcock:
Took apart the petcock and checked for integrity. The diaphragm seems to be in pretty good shape with no visible wear and tear so I'll assume all is fine here for now.

Carburetor:
Took it apart and noticed jets were stock (115 main, 17.5 pilot) but the thing was pretty gummed up so I will have to dip it for sure. According to their website, there's no Dynojet kit available for my year and model so looks like I'll need to buy my own jets. Would I also need to replace the needles?

Everything I read about pods suggests getting K&N brand. Do these really make a huge difference, or could I get away with off-brand pods I have on the bike now (not even sure what brand) with some fine tuning on the carb?

[pete]

Valve Adjustment:
Ok, I stopped by AutoZone on the way home and picked up some feeler gauges. Took the cam cover off when I got home and started checking for clearance. The intake valves were just within the lower limit (0.03mm) of clearance but for the exhaust valves I couldn't even get the 0.02 gauge between the cam lobe and shim. I read clearances on these bikes tend to get tight with wear. I managed to remove the shims (zip tie method) and noticed they were probably not the originals, as the left and right side had different thicknesses and one of the exhaust shims was put in upside down. I couldn't verify exact thickness since I don't have a caliper, but looks like I'll be needing new ones for all my valves.

Yep, the wear on these is the valve seat, which results in the valve moving up towards the camshafts and therefore the clearance decreases.

If you can't get a feeler gauge in, see if you can at least rotate the bucket easily. If you can, you need to go down one shim size. If you can't, there's no clearance at all, so you'll likely need to go down two or more shim sizes.

Shims should be installed with the marked size facing down so it doesn't wear off. If they've been installed incorrectly, you'll definitely need to work out the size.

Oh, and never rotate the engine with a shim removed.

Petcock:
Took apart the petcock and checked for integrity. The diaphragm seems to be in pretty good shape with no visible wear and tear so I'll assume all is fine here for now.

Cool. The issue I had with mine was that the metal disc broke into several pieces and turning the tap was almost impossible.

Carburetor:
Took it apart and noticed jets were stock (115 main, 17.5 pilot) but the thing was pretty gummed up so I will have to dip it for sure. According to their website, there's no Dynojet kit available for my year and model so looks like I'll need to buy my own jets. Would I also need to replace the needles?

There is a UK spec stage 3 kit E3305 but I don't know if it will be ok in a US spec bike.

Alternatively, several people have mentioned a kit at Mikes XS but noone has yet tried it so I don't know if it will work or not.

http://www.mikesxs.net/product/48-0667.html

I lucked out in that the Aus models have adjustable needles, so I've stuck with sourcing Mikuni jets here and adjusted the stock needles. I still have more tuning work to do though.

Everything I read about pods suggests getting K&N brand. Do these really make a huge difference, or could I get away with off-brand pods I have on the bike now (not even sure what brand) with some fine tuning on the carb?

K&N or APE are the way to go. The cheap ones are difficult to tune because typically they're either more restrictive than the stock airbox or they have a bad or lack of design on the intake which by all reports means they don't allow nice airflow into the carbs.

Also, cheapies don't get oiled, which means filtering is compromised compared with oiled ones, potentially allowing more crud into the carbies.

I have seen K&N's for our bikes very cheap on Amazon.

[paulorv]

Yep, the wear on these is the valve seat, which results in the valve moving up towards the camshafts and therefore the clearance decreases.

If you can't get a feeler gauge in, see if you can at least rotate the bucket easily. If you can, you need to go down one shim size. If you can't, there's no clearance at all, so you'll likely need to go down two or more shim sizes.

Shims should be installed with the marked size facing down so it doesn't wear off. If they've been installed incorrectly, you'll definitely need to work out the size.

Oh, and never rotate the engine with a shim removed.



Cool. The issue I had with mine was that the metal disc broke into several pieces and turning the tap was almost impossible.



There is a UK spec stage 3 kit E3305 but I don't know if it will be ok in a US spec bike.

Alternatively, several people have mentioned a kit at Mikes XS but noone has yet tried it so I don't know if it will work or not.

http://www.mikesxs.net/product/48-0667.html

I lucked out in that the Aus models have adjustable needles, so I've stuck with sourcing Mikuni jets here and adjusted the stock needles. I still have more tuning work to do though.



K&N or APE are the way to go. The cheap ones are difficult to tune because typically they're either more restrictive than the stock airbox or they have a bad or lack of design on the intake which by all reports means they don't allow nice airflow into the carbs.

Also, cheapies don't get oiled, which means filtering is compromised compared with oiled ones, potentially allowing more crud into the carbies.

I have seen K&N's for our bikes very cheap on Amazon.

Thanks Pete. That's a decent price on the kit but I already ordered separate jets last night. New parts will not be here until next week but I'll give an update once everything is installed.

[pete]

Cool, be interesting to see how you go.

I've been embarrassingly slack in getting back to tuning my 450, but it's proving very hard to find the time to do it...

[Mekanix]

What did you order for sizes?

[paulorv]

What did you order for sizes?

I went up 2 sizes on my main jets, so 120, but also got a pair of 122.5s just in case. For the pilot jets I only went up one size (20). They should be arriving later this week.

[paulorv]

So I finally got the parts and had a chance to work on the bike today... thought I'd post an update.

Carburetor: After installing +1 size pilot jets and +2 main jets, the bike idles great and throttle response is much smoother, though taking off in first gear still seems a bit sluggish. I am waiting to sync the carbs to see if that improves anything before trying the +3 size main jets. I ran into a bit of a problem that may not allow me to do a sync properly, though. While cleaning the carbs I got one of the adjustment screws stuck and I'm not able to turn it at all. It seems to have seized and I'm afraid to force it any further in fear of stripping the head completely. Am I screwed? Like I said the bike seems to idle just fine, but it may be effecting my initial power delivery.

Valve Adjustment: After replacing the shims with proper new sizes the heat dissipation on both sides of the engine seems to be even. I believe the cause for the right side heating up much quicker before was excess exhaust gasses being trapped in the cylinder, as the exhaust-side shim was worn down pretty bad. (That's just my guess though)

Just wanted to thank everyone for their help on this little project. Working on my GS has been just as exciting, or perhaps more, as riding it. I'll provide further updates once I have some more time to work on it.

[pete]

Good stuff!

With the mixture screw, were you turning it in or out when it got stuck? If it was turning in, it could have bottomed out and bound up, so be very careful when removing it as you don't want to break the tip off.

You definitely want to free the screw up so you can get your mixture right otherwise no amount of jet changes will be able to compensate fully for that.

It may also make synchronising the carbs a little more challenging.