Gs450 question

[tracker797]

I just replaced the head of my 450 engine 'cause the valves were burned out. I followed the manual to setup the timing but I think I got it a little off. The only thing is I'm not sure if that is what's causing all the problems I had on my test ride.

1. When it's cold, will die when I try to take off in gear (but idles fine)
2. Once warm, it takes off just fine.
3. Both cylinders back fire occasionally when I take off.
4. Both cylinders back fire when I cut the engine.
5. It feels a little jerky when it's at a constant rpm and speed (but goes away when I punch it)

Could all this be caused by the timing being off? (Probably a stupid question, but I'm a noob when if comes to working of motorcycles)

[pete]

That sounds at least partly like a fuelling problem to me.

When you replaced the head, did you do all the valve adjustments properly? That will affect this too.

My understanding is once your timing is right, you need to do the valves, and then you need to follow that up with balancing the carbs. If any of this is wrong, it won't go terribly well.

I've just finished doing the timing and adjusting the valves on my '81 450 as part of my rebuild and I'm about to clean my carbs as it's been sitting for years. Have a look at my rebuild thread if you want to see some more info on this.

There's also things like intake boots and O rings that don't age real well and will let air leaks disturb the air/fuel mixture from the carbs.

Also, make sure you have a good go through BassCliff's site at all the carb and valve tutorials, you won't regret it!

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

Also, if your timing is off, you really want to fix that soon as I'm guessing the end result may be bent valves.

[tracker797]

Thank you

Thank you for the information. I'm actually going to retry doing the timing before I ride it again. In a few weeks I'll be cleaning and rebuilding my carbs (once the jet kits get here). Hopefully that will solve my problems.

[pete]

Cool, sounds like a plan. The other thing to check out there is your fuel tap (you guys call it a petcock). There's a filter built into that and it's subject to the same gumming up as your carbs if it's left idle for a long time.