My VT700c Hates Me

[bpratt18]

Hi everyone,
I've been dealing with the same problem for a few months now and it's driving me crazy. Originally, while riding the bike it would just suddenly bog down (maybe going 50mph or so then drops down to about 30mph). Though it was dirty carbs so I cleaned them....and cleaned them and cleaned them. Still no luck. Finally I pulled the reserve tank thinking it might be full of rust, there was some but not a ton. Cleaned the carbs again using a strand of copper wire to clean out the ports, got new float needles, new pilot screws and o-rings, reinstalled and it ran a little better, but not right. Thinking I'm going crazy, I decided it would be good to get a second opinion so I brought it to my local bike mech yesterday. He started it and said, "dirty carbs". Trying to save some money I decided I'd give cleaning them another shot. Plus I work in a lab where we have an ultrasonic cleaner. Put Berryman's carb cleaner in that bad boy and let it work on the carbs for an hour each and then a rinse in plain water. They looked beautiful. Threw them on the bike today and it sounded pretty good, took it down the road and the hesitation and bogging was still there (****) and then all of a sudden I could feel the back tire swinging ahead of me. The bike literally locked up (almost like the engine seized) and threw me a good 20ft clean off. Right now the bike and I are not speaking with each other, but after I cool off it would be good to have some second (or third) opinions on what I should do next. Ohh yeah, new battery, new plugs, new plug boots, good spark, idles just fine, no pin holes in diaphragms. Thanks.

[boblamb58]

Nah, it don't hate ya. He's sick, doesn't quite know how to tell you, but the symptoms of his illness are there. It's up to you to figure it out.

[Hurg]

im gonna turn off the lights, get out my knife and take a stab in the dark.

bike has more torque in first cpl gears? makes it easier to get it moving. Then once your up to speed, and no longer opeining up on the throttle the back break is realizing it can now do its job even if not wanted. my guess is you have a problem with your back break being seized.

[CBH]

A dirty fuel filter?
Is it sucking air from somewhere?
Does it have a crack in a carburetor boot, or a fuel line?
Are the clamps tight?
With it running, spray around the intakes with some starting fluid. It will tell you if there's a vacuum leak.

[John Hopkins]

I don't think I understand what you are saying...so let's see..

you put the bike in neutral, on the centre stand, kickstand up, ignition on, choke out, press starter and the bike ticks over...are we on the same page so far?

bike warms up, choke in, bike still runs smoothly..still right?

Now the bike is ticking over at about 1K, both exhaust headers are hot engine is quite warm...does the fan start?

If the fan doesn't start do this...at the bottom of the radiator is a single wire..unplug it and touch it to the frame...does the fan start?

if the fan starts gaffatape the lead to the frame so the fan keeps running..

Now the engine is not going to overheat..

rev the engine up to about 3k..still ok?

keep the revs up for ten minutes...still ok?

Drop the revs to about 1K5 for another ten minutes..if it is still running the fault is probably nothing to do with the engine...so..

drop the revs back to 1k, pull in the clutch lever and slip the bike into first gear...Because you are on the centre stand the back wheel is off the ground and turning..can you hear grinding from the drive shaft?

gently apply the footbrake while ready to grab the clutch...does the back wheel lock on?

If not, slip the bike into second and increase the revs to 2k..does everything sound good?

Drop the revs change up and increase the revs to 2k and keep repeating until you reach overdrive, keep your hand on the clutch and run at 2K for another 15 minutes..

switch off and let us know where it went wrong..

John.

[bpratt18]

Thanks for the replies everyone. I haven't had a chance to cycle through the gears exactly as prescribed above, but this is what I know. I've had it on the center stand and even in the first gear it will stumble with throttle as well as all other gears. The snorkel (connecting the airbox to the carbs) does have cracks in it. I've plugged them up as well as I could with JB Weld, I can't imagine this really being the issue, but maybe. I used a tank liner way back and noticed red (the color of the liner) gunk in the float needle filter when I first cleaned them. Maybe some got into the ports and I haven't been able to clean it out properly?

[93gc40]

Sounds electrical, brake, and/or drive related to me. But bogging down while at speed sounds electrical. Wheel lock?? not sure the two things are related yet.

[bpratt18]

Originally Posted by 93gc40

Wheel lock?? not sure the two things are related yet.

Good point. It could be in the heat of the engine losing power and causing the back tire to drag, I forgot all my safety training and touched the brake. In that split second before I made friends with the ground, all I was thinking about was how much of an idiot I was for not letting the mech do the cleaning

[vccomputerguy]

I think John has laid out a good plan. I'd give it a try. Years ago (more than I like to admit) I had a Kawa that would go like crazy then warm up and do just what you describe. Turned out to be a overheating problem...the engine was trying to lock up.

[bpratt18]

I'll give it a shot. As soon as I can get it to turn over The key broke off in the ignition when I dropped it and so I haven't been able to check to see if it would start. I finally got the old bit out after work today, and then used the spare to see if it would turn over, just a single "click" coming from the starter...great. I'm going to take the side cover off the engine (the dry side holding the stator) and check to see if the starter drive gear or reduction gear fell off inside or got locked up or something. I'll post when I've got it running.