1980 GS450 Cutting Out 4000-7000 rpm HELP ME OUT!!! - Motorcycle-Journal Forums

Starbound · 09-19-2005, 12:15 PM

I just found this forum and hope you guys can help me out. I am working on a 1980 Suzuki GS450 that has been sitting for a long time. I have gotten almost everything fixed. I have the bike running and it runs great up to 4,000 rpm. Between 4,000 and 7,000 rpm the bike cuts out then clears up past 7,000 rpm. I have had the carbs apart 5 times and cleaned them put in new main jets etc. I did put on two K&N pod filters as the original air box was shot. I can't figure this thing out. Can anyone give me some help here, I am about to pull my hair out and I don't have a lot left.

Thank You,
Starbound

dragbar · 09-19-2005, 12:54 PM

Simple but have to ask.....Change the fuel filter? Make sure the fuel pump and associated fuel lines are cleaned out as well as a blockage can cause those symptoms easily.

Starbound · 09-19-2005, 01:10 PM

Yes it has a new fuel filter, It doesn't have a fuel pump. The tank is a little rusty inside that is why I installed the new filter. The thing is it clears out above 7000 and pulls good up to 9000 rpm. I wouldn't think it would run good on the upper if it was a clogging problem.

Thanks,
Starbound

**Clint** · 09-19-2005, 02:13 PM

My Radian used to do that, too. I'm guessing that the K&N's leaned things out a bit. You might need to adjust the jetting (more or fewer shims on the needle?).

'Nut could probably tell us.

**87gsxrnut** · 09-19-2005, 02:50 PM

Could be a couple of things. BUT, does that bike have points, or is it electronic ignition (can't remember). Most likely is in the needle circuit, but, don't rule out an electrical issue either.

- Nut

Starbound · 09-19-2005, 04:06 PM

It is electronic ignition. I was thinking that it might be in the needle circuit, but the needle is not adjustable.

ibast · 09-19-2005, 06:20 PM

Check your tank breather.

**87gsxrnut** · 09-19-2005, 07:10 PM

You still should be able to shim it.

- Nut

Starbound · 09-19-2005, 11:03 PM

Thanks for the responses guy's!! Tonight I added two shims to each needle and it did help some but still cuts out. Do you think I should add another shim or go bigger on the main jets?

Just to bring you up to speed on this bike. The bike had been sitting a long time. I cleaned the carbs, put in new 115 main jets, a new float valve in one carb and new K&N pod filters. I also added a new fuel filter, new fuel hose, new spark plugs, and changed the oil and filter. I have also sync. the carbs. Yes the fuel tank has some rust in it and I rinsed it a couple of times with gas and dumped it out.

Thanks again for the help!

Starbound

09-19-2005, 12:15 PM	#1 (permalink)
Starbound Newbie Joined: Sep 2005 Location: Marshfield, Missouri Posts: 4	1980 GS450 Cutting Out 4000-7000 rpm HELP ME OUT!!! I just found this forum and hope you guys can help me out. I am working on a 1980 Suzuki GS450 that has been sitting for a long time. I have gotten almost everything fixed. I have the bike running and it runs great up to 4,000 rpm. Between 4,000 and 7,000 rpm the bike cuts out then clears up past 7,000 rpm. I have had the carbs apart 5 times and cleaned them put in new main jets etc. I did put on two K&N pod filters as the original air box was shot. I can't figure this thing out. Can anyone give me some help here, I am about to pull my hair out and I don't have a lot left. Thank You, Starbound

09-19-2005, 02:50 PM	#5 (permalink)
87gsxrnut Ho Dog Joined: Dec 2003 Bike: 867-5309 Location: Terror Lake Posts: 4,224	Could be a couple of things. BUT, does that bike have points, or is it electronic ignition (can't remember). Most likely is in the needle circuit, but, don't rule out an electrical issue either. - Nut __________________ Person or person's unknown.

09-19-2005, 07:10 PM	#8 (permalink)
87gsxrnut Ho Dog Joined: Dec 2003 Bike: 867-5309 Location: Terror Lake Posts: 4,224	You still should be able to shim it. - Nut __________________ Person or person's unknown.

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09-19-2005, 12:54 PM	#2 (permalink)
dragbar Fifth gear streak Joined: May 2005 Bike: M50 Location: SE Missouri Posts: 1,375	Simple but have to ask.....Change the fuel filter? Make sure the fuel pump and associated fuel lines are cleaned out as well as a blockage can cause those symptoms easily.

09-19-2005, 01:10 PM	#3 (permalink)
Starbound Newbie Joined: Sep 2005 Location: Marshfield, Missouri Posts: 4	Yes it has a new fuel filter, It doesn't have a fuel pump. The tank is a little rusty inside that is why I installed the new filter. The thing is it clears out above 7000 and pulls good up to 9000 rpm. I wouldn't think it would run good on the upper if it was a clogging problem. Thanks, Starbound

09-19-2005, 04:06 PM	#6 (permalink)
Starbound Newbie Joined: Sep 2005 Location: Marshfield, Missouri Posts: 4	It is electronic ignition. I was thinking that it might be in the needle circuit, but the needle is not adjustable.

09-19-2005, 06:20 PM	#7 (permalink)
ibast Where Am I ? Joined: May 2005 Bike: GSX-R1100 Location: Sydney Posts: 32	Check your tank breather.

09-19-2005, 11:03 PM	#9 (permalink)
Starbound Newbie Joined: Sep 2005 Location: Marshfield, Missouri Posts: 4	Thanks for the responses guy's!! Tonight I added two shims to each needle and it did help some but still cuts out. Do you think I should add another shim or go bigger on the main jets? Just to bring you up to speed on this bike. The bike had been sitting a long time. I cleaned the carbs, put in new 115 main jets, a new float valve in one carb and new K&N pod filters. I also added a new fuel filter, new fuel hose, new spark plugs, and changed the oil and filter. I have also sync. the carbs. Yes the fuel tank has some rust in it and I rinsed it a couple of times with gas and dumped it out. Thanks again for the help! Starbound

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