This is a post to explain an easy solution to a problem I battled for months. I'm not meaning to start a discussion just basically streamlining an earlier post I made about not being able to get up over 4500 RPM.
The problem: after assembling a bike I got with the carbs, airbox, and exhausts off I found I couldn't get the bike to rev properly. Until 4500 RPMs or 1/4 throttle, whichever came first, the bike had plenty of power...then nothing. If I opened the throttle too much the bike would start to engine brake, at WOT it would engine brake down to about 2000 rpms then surge and engine brake at about one second intervals.
The solution: obviously many things could cause a similar problem like dirty carbs, petcock issues, dips in the fuel line, improper airbox install, faulty coil, bad spark, trigger wheel or pulse gen problems, bad compression ect... in my case I had hooked the carb vent tubes up to the airbox.
An explanation of what that means: if you look at your carbs there are joiner tubes that run between 1-3-5 and 2-4-6, which are the two seperate carb sides or banks. 2-4-6 are on the clutch side 1-3-5 on the brake. On each bank two of those tubes will be a plastic T and two will be strait plastic tubes. The carb vents are the top row's plastic Ts, the ones closer to the airbox, they are the smaller Ts. From there you should have two hoses...if the hoses come to a T then to the petcock, you have the wrong hoses, those are the fuel lines. The ones you're looking for shouldn't attach to anything, if they go anywhere it should be to the two holes in the rear-most carb bracket. They just go to open air.
What happened with my hoses is that the PO had led them to a T and then put a third hose leading off from there. When I saw that I assumed the hose leading out of the T went to the airbox, afterall there are three nipples coming off the bottom of the airbox and one was still available.
Of those nipples One should line up perfectly with the crank-case breather container (plastic box directly behind the ignition switch) the second generally leads down to the PAIR valve or if your bike is de-smogged it should be blocked off, the last and smallest hole is the airbox drain. I had hooked my carb vents up to the airbox drain.
To fix the problem: All that needs to be done is for the carb vent hoses to be disconnected from the airbox. From there you'll need to run the hose from the airbox drain to its proper place. Its proper place is to a T connection with the reddish drool tube and a short hose that leads from the bottom of the crank-case container behind the ignition switch. In my case the PO had removed the plastic T and the short hose that led from the container to the T.
Check out this fiche if you need a clearer picture:
https://www.partzilla.com/catalog/honda/motorcycle/1998/gl1500c-a-valkyrie/air-cleanerthe container is # 10
the hose connecting to the airbox drain is # 23
the T connecting the drool tube to container and airbox drain hose is # 1
drool tube is #24
short hose between container and T is #9
for an explanation of why this happens when the vents are hooked up to the airbox read the last few replies from pancho and meathead on page three of this post.
http://www.valkyrieforum.com/bbs/index.php/topic,109080.80.htmlFeel free to ask any questions.
