Evening all. I took possession of my CBR 1000F yesterday, 1990 model, and have a question regarding the exhaust and the way the bike should run. It has a Vance and Hines 4/1 SS2 system installed and it sounds sweet. However, it seems to stumble between 2000-2500 rpm, then it comes on strong. The mechanics at the bike shop said it was running fine and seemed to be jetted properly. I not familiar with these exhaust systems as I have always ran stock systems on the bikes I've owned. It runs great when I'm in the power band, but when I'm in lower gears just cruisin, it seems to run rough, almost like a big cam would act, if that makes sense. Is this normal or should I take it back to shop and have them look it over again. It doesn'
t run bad, just not as smooth as I expected it should. I would also like to ad that of all the bikes I have owned over the years, and the count is high, this CBR 1000 is by far the sweetest ride I have had in a long, long, time. It's fast, comfortable, and rides like it's on rails. Of course, you all know that. Thanks for listening.
Peace
Don

 

That does sound like jetting problem. A couple things you might try. First, since the shop tells you the jets are okay, synch your carbs. If that doesn't cure things do a chop check on your plugs. Find a stretch of road where you can run the bike in whatever gear you're having trouble at the rpm that shows rough running. Keep it at that speed for a couple minutes, then pull in the clutch and hit the run switch to off. Coast to the side of the road, raise your tank and pull the plugs. Are they sooted (not oiled) up? Wet? That means running rich. Are they bone white? You're running lean. Either most likely is a carb problem. If the plugs are running light tan, you're okay. Although running rough at only one specific rpm doesn't indicate it, you might check the air cleaner, the plug wires and the plugs themselves. Finally, and most drastically, I solved sort of the same problem on my 1000F by having the valves ground. I say 'sort of' because not only did it run rough at lower rpm, it didn't have its old power at higher rpm. One intake was pretty bad, another kinda bad. To figure that out, do a compression check. If you are off by more than 10% cylinder to cylinder or if compression is generally low drip a little oil in the cylinder, crank it over a few times, and redo the compression test. A dramatic rise in compression indicates worn rings. A not so dramatic rise indicates bad valves. You might also do a leak down test. That can tell you if you have bad intake (blows air through the carb), exhaust (blows air through the exhaust pipe) or rings (you can hear air at the oil filler). It's a near 100% probability that valves/rings are not your problem. I'm betting it's the carbs.

Oooh, oooh, I forgot. If you do a compression check be sure to set the kill switch to 'off' before cranking the engine over. It's possible to kill the CDI by cranking with switch on 'run' and the plugs not grounded. Honda's price for one of those is $550 or so.

 

DRam, Thanks for the advice. I'm thinking it's the carbs, or rather hoping, it's the carbs. The bike only has 20,000 miles. I will pull the plugs and give them a look. Thanks again.
Peace
Don

 

Only 20K miles? Great buy. By the way, if it's been sitting for some time there is the possibility of gunk in the carbs.

 

Can't tell you if the bike sat much or not. Obviously, with only 20 grand on the odometer, it didn't get ridden near enough. I do know it came from Anchorage, Alaska. Maybe that explains the milage. The body is in fantastic condition and I will get some pics posted soon.
Peace