Honda 81 CB650C

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nu_bronco · #1 Unread post by **nu_bronco** » Sun Sep 03, 2006 9:25 am

I noticed that the bike loses power/sputters at about 5,500 RPM. It won't go more than 60 MPH on the speedo (which I have been told I am only doing 55). I tried in the other gears also all with the same results, 5,500 RPM and it sputters and surges.

I have cleaned the carbs and I have pulled off the petcock (which cant be disassembled). Does anybody have any suggestions? I have seen a few similar looking discriptions so hopeful someone will have the answer.

Thanks for any help in advance.

blazercrx · #2 Unread post by **blazercrx** » Mon Sep 04, 2006 2:31 am

I own a cb 900c and have the same problem at that rpm. I did a rebuild on the engine and ended up keeping the same valve lifter springs, the only thing that I can think of is that the springs are weak and at that rpm the valves are starting to float. I could be wrong, but after 25 yrs. of compressing springs they tend to weaken.

nu_bronco · #3 Unread post by **nu_bronco** » Mon Sep 04, 2006 3:01 am

thanks for the input. I don't know a lot. But this only happens under a load, meaning only when I am riding. I can just have the bike in neutral and I can rev the engine beyond that rpm range with no problem. Is yours the same way?

blazercrx · #4 Unread post by **blazercrx** » Mon Sep 04, 2006 6:50 am

ya, but not not too much further than 6500 rpm.

oldschoolorange · Mon Sep 04, 2006 9:20 am

do a tune up ( set lifters and change+gap plugs) I have had bad plugs screw things up like that

blazercrx · Mon Sep 04, 2006 10:26 am

I just took mine for a ride and reved it in neutral and it did rev all the way to 9000 and started sputtering around 5500 while in gear. I know that I have already done the tune up and checked gap on valves and plugs and it still does it. I've even done a compression check and they're all 100 across the board! I've had the carbs cleaned and synced, in my situation everything that I can think of has been taken care of. Maybe one of these things could be nu_bronco's problem though.

nu_bronco · #7 Unread post by **nu_bronco** » Mon Sep 04, 2006 1:03 pm

I have cleaned the carbs, but didn't disassemble completely because I don't have the tool to sync them and have never done so. I got the bike about a month ago now and have just been taking back roads to work but could save 20 minutes each way if I can figure this problem out. I have checked the valves but my friend says I need the valves adjusted. I will have to pull the plugs and check them out as far as the gap and see what color they are....at one time I had some pictures of good and bad plugs and depending on the picture you could help judge what the issues were with the fuel mixture. Anyone have any pictures or know of a link for examples?

Thanks for the help guys.

nu_bronco · #8 Unread post by **nu_bronco** » Mon Sep 04, 2006 1:05 pm

sorry another questions, when you disassembled the carbs completely, when you put them back together how did you spread the screws that you have to file down to seperate the carbs from each other? Thanks.

nu_bronco · #9 Unread post by **nu_bronco** » Thu Sep 07, 2006 2:56 am

Is there a way to test the ignition coil? I just looked online and these are about 100 a piece and I could possibly need two but not sure if that is causing my problem. I would like to not spend that much because I only paid 500 for the bike.

Anyone think this could be causing my problem?

oldschoolorange · Fri Sep 08, 2006 10:53 am

you can test coils with an ohm meter, However heat can affect them so your reistance could change when they get hot. test a new one to get a spec then test yours, In my experiance it is very rarely the coil