surging/slipping problem while riding

[Anonymous]

I recently revivied my 88 GS450 after a three year nap. I cleand the carbs, installed a fuel filter, checked the valve gap/lash (which was correct), rebuilt fuel selector valve with new diaphragm, and the bike was running great.

Now to the problem, recently while riding I noticed the engine was surging/slipping while at hwy speeds 50-70 mph ( ihave not tried to determine if it is present faster than that). This was not present before and I am inclined to think that this is a new developing problem. I think I will try the usual ie.. WD-40 around the gaskets, check the fuel filter, air box, but do you guys have any other suggestions?

Nathan

 

[Anonymous]

Please define the symptoms a little different. Surging from a vacuujm leak only happens at idle on these bikes, since there's really nowhere "above" the throttle plate for a leak. Slipping sounds like the clutch. Is it "hesitating" or missing at those speeds? If so, i'd like to know what happens when you open the throttle all the way up at those speeds. At those speeds, you are usually running on the pilot jets, so perhaps some grunge is in the carbs again? It can really be any number of things including carb synch.

Tim

 

[Anonymous]

Missing would probably describe it better than surging, while I am riding I notice the engine has a miss, it feels like it is loosing power than it gets it back. Tha is while I am at a constant speed and do not open the throttle. If I open the throttle it heitates for a second than picks up. I also forgot to mention that at idle when cold if I hit the accelerator very slightly the bike will backfire very slightly. this very rarely happens thopugh. Maybe this will be a better description.

Thanks
Nathan

 

[Anonymous]

It does sound a bit like surging. Sometimes surging can be caused by incorrect settings on the air mains. If you took the carbs apart you may want t o try and tune them in a bit. An easy way to test this is to cover half of your filter and ride at the speeds that you felt the surging and then try it with the filter out. From the results you can determine what the problem is. That is if it is surging.

 

[Anonymous]

alright, thanks I will check into that soon, will post a reply when finished.

Nathan

 

[Anonymous]

I think I know what you are talking about... Let me tell you what I am hearing, you tell me if I am right: You are riding down the highway at regular highway speeds "cruising". i.e. not accellerating, not slowing down. You feel the bike mildly buck. Almost like you are running out of fuel, but not quite.

The very first thing I do when I see this problem is yank the carbs, and clean the things. I'd pay CLOSE attention to the pilot jets. When you open the throttle up, it starves for a second, until the mains pick up the load, then it goes. Once again, pilot jets are suspect.

Tim

 

[Anonymous]

That was a very good description of the problem I WAS experiencing. I did take a look at the carbs. There was some very small particles of gunk present. I cleaned them out and have not experienced the problem since.

Thanks
Nathan