GS450 Engine Won't Start

[jmaresca]

I'm just about finished rebuilding my gs450. I just need to get the engine sorted out. It won't kick over. It did for a few minutes, the first time I went to start it, then died. I would have to pull the throttle to get it going, it wouldn't idle.

What I've Done:

Carb dip
Rejet to 142.5 Main, 45 Pilot
K&N Oval Filters
Oil Change
Open pipes

Fuel is making it into the carb. The left coil is getting 11.64 volts. The right is getting 10.6 volts. Both new plugs are sparking when grounded. I noticed I had the top breather hole on the engine plugged from when I painted it. I removed that and It still won't start. I checked the oil and it's fresh. What should I try next?

 

[eil]

10.6v is a little low, so definitely look into that, maybe a coil relay mod is in your near future. But if you get spark, it should at least be trying to start. Random ideas:

- valve clearance adjustment?
- idle adjust screw set too low?
- what do the plugs look like after failing to start?
- mixture screws too rich/lean?
- compression test?

 

[jmaresca]

10.6v is a little low, so definitely look into that, maybe a coil relay mod is in your near future. But if you get spark, it should at least be trying to start. Random ideas:

- valve clearance adjustment?
- idle adjust screw set too low?
- what do the plugs look like after failing to start?
- mixture screws too rich/lean?
- compression test?

I haven't done a valve adjustment yet. I found a tutorial on BikeCliff's here, but that's for an 850. The idle adjust screw is fine. After failing to start, the plugs still look brand new. I've tried the mixture screws at everywhere from 2 turns out to 5. I haven't done a compression test either. I don't have a tester.

I figured the valves and compression should be fine if I was able to get it started originally. At that point I had my mixture screws out 5 turns. When I turned them in down to 2 is when it wouldn't start again. I'm wondering if I went too rich in my jets.

 

[jeffasaurus2]

While it wasn't the case for me, I've read that the stock pilot will usually be OK for Pods/Pipes. 2~2.5 turns out on the mixture screws is a perfect starting point, I really wouldn't mess with them until the bike was at least idling.

Can't remember if you went through the carbs but did you bench sync the carbs? If they're too far off from each other it would definitely cause issues.

The valve adjustment is something to look into, at the very least, check. The procedure for the 850 is the same for the 450, just a couple less valves to check. Only thing to really make sure of is the cam lobe position before you measure the clearance.

 

[jmaresca]

While it wasn't the case for me, I've read that the stock pilot will usually be OK for Pods/Pipes. 2~2.5 turns out on the mixture screws is a perfect starting point, I really wouldn't mess with them until the bike was at least idling.

Can't remember if you went through the carbs but did you bench sync the carbs? If they're too far off from each other it would definitely cause issues.

The valve adjustment is something to look into, at the very least, check. The procedure for the 850 is the same for the 450, just a couple less valves to check. Only thing to really make sure of is the cam lobe position before you measure the clearance.

I actually also read you can get away with stock pilots. But I also read you should rejet pilots. I bought a slew of main jets (137.5 to 147.5) and pilots (42.5 to 47.5). I think I should try the stock pilot with the 137.5 main. I did bench sync the carbs.

 

[tkent02]

I figured the valves and compression should be fine if I was able to get it started originally.

Adjust the valves.

 

[jmaresca]

Adjust the valves.

I'll do this and set the jets back to stock just to see if I can get it running, then go from there.

Just to be sure what I'll need to do this, does this sound right?

19mm socket
shims (29.5mm from Z1)
new gasket
new breather gasket
shim tool

 

[jeffasaurus2]

You wont know what shims you'll need until you've checked what shims you've got. There's a range of available shims.

You don't necessarily need a breather gasket, you can get away with leaving it on the cover. You'll also need feeler gauges that have a range between 0.03mm to 0.08mm.

 

[jmaresca]

While looking over my spark plugs, I noticed my left spark is an orange spark instead of a blue spark. Is this indicative of a bad left coil? They're brand new plugs.

 

[jmaresca]

Bought an extra shim and checked all of my sizes:

Front Left Exhaust: 2.65
Front Right Exhaust: 2.70
Back Left Intake: 2.55x
Back Right Intake: 2.55x

I tried swapping them around even going from the 2.70 to the 2.55x. Still couldn't fit my .038 mm feeler gauge. After swapping the shims around, 3 of the 4 spin, but my smallest feeler still won't fit on any of them. I'm using Steve's spreadsheet, and all 4 are saying to go down .05, but I feel I need to go down more. I'm guessing the spreadsheet only applies if you can actually measure rather than entering .01 mm for clearance?

Does swapping one shim affect the fit of the other three?

Should I be looking for a .05 mm clearance on intake and .10 mm clearance on exhaust?

PS: whoever came up with the zip tie trick is one clever SOB.

 

[Guest]

Just to be clear... when measuring, the cam lobes are pointing either perpendicular or parallel to the valve cover gasket surface right?

One shim won't affect the others, but if you have one cam lobe pointed the right way to check clearance and the other lobe of the same cam is pushing down on the other bucket, that affects the clearance reading of the one you're measuring.

Make sure neither lobe of the cam you're measuring is pushing down on a bucket.

I hope that makes sense...

 

[jmaresca]

Just to be clear... when measuring, the cam lobes are pointing either perpendicular or parallel to the valve cover gasket surface right?

One shim won't affect the others, but if you have one cam lobe pointed the right way to check clearance and the other lobe of the same cam is pushing down on the other bucket, that affects the clearance reading of the one you're measuring.

Make sure neither lobe of the cam you're measuring is pushing down on a bucket.

I hope that makes sense...

That does make sense. I was actually taking readings with the lobe perpendicularly away from the shim I was measuring. The way you describe it makes sense. I just measured my 5 shims and they are pretty much all on point. My 2.55x are 2.58 mm. When using the 2.55x's, all 4 spin, but I still can't get my smallest feeler in there (.038 mm). I think I should be able to order 4 2.50 mm shims and be done with it.

 

[Guest]

I made that same mistake the first time and thought ordering 4 shims couldn't be right... checked the manual again, face palm, and only had to order 1 shim