I've screwed something up -Idle issue

[MSGJONES]

I've always been able to search forums to solve issues I was having without asking questions but after searching for a week I'm still no closer to solving my problem, so here it goes. I recently bought a 2000 VMAX with 7081 miles, cosmetically in fantastic condition. It hadn't been ridden for seven years because 2nd gear was out. I've worked on and rebuilt all kinds of engines over the years so I was not worried about tearing into this one. I put a new battery in it, changed the oil, put in fresh gas, and it started immediately. After it warmed up I took it off choke and it settled in around 1000 RPM. I put about 170 miles on bike tiptoeing around 2nd gear. The bikes motor was running perfect, vboost worked as it should and throttle response was great. All I'm trying to convey is the bike was running perfect before I tore it apart. I pulled the motor, turned it upside, and pulled the bottom off exposing the transmission. I didn't break any electrical connectors, hoses, or bolts. The gears looked really good but the shift drum was badly worn in the 2nd gear grove so I found a nice used one on eBay and I just had 2nd gear undercut for good measure. I reassembled the engine with new gaskets and reinstalled it. I used dielectric grease on all connections. The bike started right away, I let it warm up then took it off choke. It tried to idle but then went up to 4000 RPMs, I burped the throttle and it came down briefly then shot back up. The bike coughs through the carbs and pops out the exhaust. Immediately I assumed an air leak causing a lean condition so I checked to see if any clamps were loose, they weren't. I used starting fluid to check of leaks but found none. I checked all electrical connections and found nothing. I synchronized the carbs which made no difference. I ordered all 8 rubber boots for the carbs and vboost, installed them, paying attention to their orientation with no change. I then pulled the carbs off, inspected for bent rods or damage, cleaned them, reinstalled, and synchronized again (carbs were spotless inside all jets were open) but made no difference and remember the bike was running perfect before I tore it apart. I installed new sparkplugs and the plastic coolant bolt has the OFF pointed at the 2 o'clock position after bleeding. It has new coolant and is toped off. The latest condition is the left front chrome header is turning blue from what I think is a lean condition on that cylinder. If you start the bike from cold and hold onto the headers the left one heats up much faster its also the cylinder with the hose going to the Intake Pressure Sensor. On a good note I did take the bike for a ride and as hard as I tried I could not get it to jump out of 2nd gear so I think the trans is fixed. I don't understand what I did to cause the bike to run this way, any ideas would be greatly appreciate.

 

[gentsvmax]

Hey MSGJones, one thing for sure is you did a great job laying out the issue and steps taken so far.
Excellent job getting right in to get that second gear handled!
Try removing the rack(carbs) and put them on your bench, check that
they are all four setting flat. Maybe loosen then tighten both side, two top
and the two bottom plates on the off chance the rack got distorted during
the r&r . I know you sprayed it but cant hurt to check. How bout those sync
ports, are nipples sealing tight? Dam, cant really think of anything you didnt
already cover.

 

[Fire-medic]

As gents Vmax said, you did a great job of describing the problem and what you've already accomplished. Unfortunately I agree with the two of you that it sounds like you've covered everything you need to cover yet the problem still persists. My experience has been that a good synchronization takes care of a wandering idle such as you have described. Another possibility due to age of components would be the rubber Donuts from the airbox to the car Belmonts and from the bottom of the carbs to the v-boost but again you have already addressed that. Using the starting spray to search for leaks on the intakes is what I do and you say that you haven't seen anything turn up as a result of you're having done that. I had something similar to yours, I bought a 1993 offer retired military veteran and it only had 10,000 miles on it. The idle was hanging up and it turned out to be one of the very thin O-rings beneath the v-boost where it bolts to the cylinder intake. One was bad/leaking and of course I replaced all four which after a good synchronization fixed things up perfectly. Tell us what you did with the carburetors, did you give them an ultrasonic bath? I know that most of the time a single bath does it but on occasion if, as in your case, poor running persists, back into the ultrasonic tank go the carburetor bodies.

I expect that you were very diligent and careful about making sure that the donuts had the airbox well-seated into the top ones and the carburetor bottoms inserted into the bottom ones. I have seen on used bikes that I've purchased where the insertion depth of the airbox or the carburetors into the rubber Donuts has not been to spec. I expect that this is not an issue for you since you have eight new Donuts and seem to be very much on top of proper installation. Another thing that I've seen is that people are not tightening to spec the clamps for the donuts.

About the only thing that I haven't heard mentioned in the discussion here is something having to do with the four carb cables. Having one of those Motion Pro cable oilers is a good way to take care of making sure that you have adequate lubrication.

As you are probably aware, a pinched cable metal housing can hang up the inner cable and cause problems with running. Another possibility is that the routing of the cables is creating a pressure point somewhere where the inner cable and the outer cable may not be moving freely. The service manual is instructions and pictures about how to route the throttle cables.

Another possibility is lack of adequate free play in the cables which can definitely cause the cables to hang up and cause sky high RPMs. I suspect those may not be affecting your ride since you seem to be on top of things. I will be interested to see what others suggest and with your persistence to track down the offending issue what it ends up being. Good luck.

 

[Stephan]

I can't help thinking that it is no coincidence that it is the front left cylinder running weak and that is the only cylinder which does not have a blind plug on the vacuum take off. You have mentioned that of course, but not whether you have checked out the various connections for that vacuum hose, and indeed the hose itself. Maybe you have, but if not I suggest a close look.

 

[MaxMidnight]

The bike started right away, I let it warm up then took it off choke. It tried to idle but then went up to 4000 RPMs, I burped the throttle and it came down briefly then shot back up. The bike coughs through the carbs and pops out the exhaust.

This is the relevant part of your post.

As Stephan suggests, you need to investigate why the one cylinder appears to be running lean.
If you re-apply the choke (partially or fully) do the the revs come down?
What does the plug on that cylinder look like relative to the others?
What happens if you pinch the hose to the advance unit?

 

[MSGJONES]

Thanks for taking the time to give your suggestions. I’ll check for vacuum leaks again, check cables, and resynchronize using steps I found in the forum. I just struggle understanding how it went from running perfect to the way it is now. When I removed the carbs I just set them down on the table and they stayed there until in put them back on I didn’t even drain the fuel out of them so how could they have gotten Messed up? The o rings on the intake manifolds looked good and I put a little yamabond on them to help them seal.

 

[putin]

Thanks for taking the time to give your suggestions. I’ll check for vacuum leaks again, check cables, and resynchronize using steps I found in the forum. I just struggle understanding how it went from running perfect to the way it is now. When I removed the carbs I just set them down on the table and they stayed there until in put them back on I didn’t even drain the fuel out of them so how could they have gotten Messed up? The o rings on the intake manifolds looked good and I put a little yamabond on them to help them seal.

Bike had not been ridden for 7 years? Your carbs must be dead, then. We all rebuild carbs here from time to time. And problems with carbs appear from nowhere.

 

[wayne billings]

MSGJONES HI I don't mean to over simplify , but I had a similar thing happen to me not that long ago. When I reinstalled the carb rack I had to lube the rubbers and make a real effort to get all 4 into there places. My first efforts resulted in a similar result of the engine popping thru the carb and exhaust and one or two cylinders not warming up as normal. All because they were not all in place.I hope it is that simple . Cheers p.s I know when they are not correct is the faux tank cover is difficult to install.

 

[MSGJONES]

The plug from #2 cylinder did have more of a white ish color than then the others. I did put some dielectric grease on the boots to help them slide on easier. I used half a can of starting fluid looking for leaks and found nothing. I gaped new plugs and installed them. I also synchronized the carbs using Dannymax’s procedure. The bike seams to be running better. It’s supposed to be nice here in Ohio Wednesday so I’m going to detail it and ride it to work and see how it goes.