[hpp]

Hi. I am having a problem with my 1982 CM450C. I got the bike form a friend who told me the bike was sitting for more than 10 years in his garage without being started. Only 2k miles on the bike. Ran great before it was put away. I gave the bike a once over and have been trying to get it to run correctly. For the fuel system, I disassembled the carbs and cleaned everything. Also, cleaned the gas tank, but have been primarily running the bike with just a fuel bottle hooked up.

The bike idles perfectly. It runs pretty well under full throttle. The problem is that it surges badly at constant RPM and constant throttle. In neutral, if I rev it to 3000 RPM, the bike will surge to 4000, then stumble to 2000, etc. When cruising around the block at low to mid-speeds, the same thing happens.

I've taken the carbs apart, cleaned, and reassembled 6 times now, but with the same results. I'm hoping that some of the experts in the forum can point me in the right direction to solve this problem.

I was careful to always put all adjustment screws back to their starting positions. I didn't alter any of the adjustments. I didn't do anything with the sync adjustment either.

Thank you in advance.

Rick

 

[66Sprint]

You first must sync and re-set the carbs...Variance at a constant throttle indicates an "out of sync" condition......
1/16 of a turn is enough to cause a major change , and it's easy to be "off" that far when re-installing screws, no matter how careful you think you were.....
This of course also presumes the carbs are scrupulously clean.....MANY clean their carbs three or more times before that occurs....(I believe 10 times is the record....LOL....)

 

[J-T]

My suggestion is to start with a quiet evening, a comfortable recliner, a large cooler (full, of course), and this:

http://www.hondatwins.net/forums/63-fuel-supply-carburation/24191-rebuilding-vbulletin-carbs.html

I moved your post to the SOHC section where you can find this along with a lot of other great stuff related to your bike and it's carbs.

Welcome to the group.

Got pictures?

 

[longdistancerider]

While in the carbs did you happen to check the needle number? As per the Honda Service Bulletin http://www.hondatwins.net/forums/63...2-honda-service-bulletin-450-drivability.html they should be 61C needles specifically designed to deal with an even throttle surge. That's not to say this is the cure but they do need to be checked and the sync and mixtures do need to be set correctly.
Do you have the Honda FSM? factory service manual

 

[hpp]

Thank you for your replies.

Jim - No, I didn't check the needle numbers. If/when I take the carbs apart again I will look. Thanks.

JT - thanks for moving the post to the correct forum. I'll look over the info you pointed to.

Stephen - Because it idles so well, carb synchronizing was out of my radar a bit, but maybe this is it. I read about this in JT's info.

Here are a couple of pictures.

 

[J-T]

Nice bike!

 

[dtsmjr8dan]

Yes. That bike is in great looking shape.

 

[hondafanatic666]

Thank you for your replies.

Jim - No, I didn't check the needle numbers. If/when I take the carbs apart again I will look. Thanks.

JT - thanks for moving the post to the correct forum. I'll look over the info you pointed to.

Stephen - Because it idles so well, carb synchronizing was out of my radar a bit, but maybe this is it. I read about this in JT's info.

Here are a couple of pictures.

View attachment 51139 View attachment 51140

Hey if u need some parts I'm chopping my frame up what ever doesn't get used ill let u know

 

[Jooknon]

Thank you for your replies.

Jim - No, I didn't check the needle numbers. If/when I take the carbs apart again I will look.

JPP-

You can pull the needles out without removing the carbs. Just remove the two screws on the cap, remove it and and the needle will come up with the slide.
FYI the 61C Needles are very hard to find. I'm still looking for one more for my bike. I think the post Jim linked to above has the mod I did to help lower the amount of surging with 61A needles.

Ben