loosing power

[Guerrero]

Bought new battery.put it on-cold without turning acceerator,without choke from half turn it started  ::) yeyyy

[Guerrero]

Hmm.but still have some little problems with power-till about 4.5k rmp it kind of looses  :-\

[pinholenz]

That is about the rpm range where the famous "stumble" kicks in. Does it drive through this and is OK at higher revs?

[Guerrero]

Yes.after about 4-4.5 k it gos up to maximum like adevil :) but till that :'(especially at first gear. Is it possible to do something about that?because problem is not only that it goes slow at low rmp,but itkind of jumps.full power/half of it

[pinholenz]

You are not going to like this - Its the carbs!! Its the carbs!! Its the carbs!!

Blocked idle circuit, and/or air leaks into the carbs, and/or accelerator pump settings, and/or carb sync, and /or flapper vacuum. - the list goes on. Each time you thoroughly clean the carbs it will improve a bit until eventually it doesn't  cause you as  much grief. Good luck

[Guerrero]

 :(sounds bad...oh well...will have to try fix this all.thanks for the info

[Guerrero]

So.just cleaned my carbs.changed some vacuume tubes.little bit.better.but still has problem with acceleration.so what should he my next step?how can i sync?although carbs were synced,and i did not changed anithing now

[pinholenz]

Hi Guerrero,

If you have done a REALLY REALLY full and proper carb clean then you will have had to have changed things, including the carb sync.

Before you strip the carbs out again, with the bike running, squirt carb cleaner at all the joints around the carb boots and each end of the butterfly shafts. Any change in RPM indicates an air leak and has to be sorted.  Do the same with each vacuum outlet joint.

With the carbs out, every plug and every jet and each emulsion tube has to come out, including those jets buried deep in the body and the low speed air mixture screws. Strip the accelerator pump and check that it is not got a hole in it and it is delivering to each nozzle. If not strip out the nozzles and check the ball underneath is moving freely. Check that the nozzles are aimed correctly between the  carb throat and the accelerator butterfly.

Squirt carb cleaner down every hole 2 or 3 times. Then blow them out with an airline before reassembling Check float heights and check wear in the float valve jacket and "o" ring. Replace any broken or worn "O" rings throughout the carb. If there is any rust sludge in the  float bowls, install an in-line filter. (I put rare earth magnets in my float bowls to catch any rust - I  have a crappy tank)

Every internal part of the carbs has to be pristine clean with no air leaks. Then you can start tuning and syncing the carbs.

Good luck.

[Guerrero]

Hello .im back:) tried different things,and now finaly disconnected the wire you talked about-rmp limiter.from front,under speedo.and it seems it really helped.i could drive on first gear even without problems,without power loose.question is-what does it mean?what should i do?what exactly do rpm limiter means?(the rounds can go higher that allowed,or what? And can i just drive with disconnected that wire?

[pinholenz]

That's good news. For most Vision owners, disconnecting the rev. limiter is a standard procedure. Mine was already done when I got my bike. A bit like the kick stand switch , it is a fail safe mechanism. Apparently if detects if the engine over-revs and cuts power to prevent engine damage. However the mechanism can become faulty and power can be lost during normal operation - hence most owners just disconnect the wire to prevent the risk of problems.

You do not need to do anything apart from covering the wire ends with insulation tape to prevent any accidental connections with other wires. It seems most owners would disconnect the yellow/black wire from near the TCI unit because of the easier access than at the back of the speedo. Either end is fine. Hope that the ride is more enjoyable now.

All the best

[Rikugun]

the rounds can go higher that allowed,or what? And can i just drive with disconnected that wire?

Yes, the engine now has the potential to over-rev under some circumstances where it may not have before. You can still ride it (and many do) but you must exercise a bit more care now.

[Rick G]

I had mine to 11500 with no p problem . The rev limiter cuts the  spark intermittently on the front cyl. At 12000. Unless you plan to rev it higher than that , you will not notice a difference!

[Rikugun]

I had mine to 11500 with no p problem . The rev limiter cuts the  spark intermittently on the front cyl. At 12000. Unless you plan to rev it higher than that , you will not notice a difference!

That's a good point in that the advertised redline does not include the engineered safety factor. Of course as the valve springs age and fatigue, the safety factor diminishes.  Also, it's not always the planned over-revving that is destructive but rather the unplanned over-revving. You know, like the unintentional missed shift at 12k. The resultant smiley faces left in the piston crowns by the valves will be nothing to laugh about!   :o  :(  :D

[Guerrero]

Hello again.
So,finaly got new carburetor kit.installed everithing.and now atleast the rmp on neutral are not jumping up and down.and bike is even drivable.but still,i cant get constant speed,because if i dont change throttle,the power is loosing.and not all time when i accelerate it is rewing up.carb has been cleaned once again with ultra sound.
Do you have some ideas,what next should i do? or maybe i can take a little video with my bike,and show to you?
the thing is,my master who repaired ,is really good,but he saw bike like this,for first time,and have no close ideas,how to get it run nicely.maybe you can give me some more advice?it would be just great :angel:

[Rick G]

I've never heard of a vision kissing the piston crowns with the valves .  The springs are getting older , that's true  but this bike had the stoutest valve train I've ever seen on a bike. I suspect that the design team at Cosworth  over engineered  the thing, too bad Yamaha didn't build it in the original 780 cc configuration. I wish I could get a hold of the fellow who was racing the Vision tracker , he would be  able to educate us on that  .

[Guerrero]

You want to say,that my vision has piston crowns kissing with the valves?sounds not so good,and what should i do then?

unfortunately ifor now,my bike is like a disaster  :(everywhere are some problems.just want to get it ridin normaly.

And btw,i still got fuel usage problem.it is just too high.

[Guerrero]

just found out,that there should be carb vent hoses ??? ofc i dont have them.hm.are they necessary?i understand where they connect to carbs,but where exactly do other end goes to?

[Re-Vision]

The two hoses should come from the front and rear carbs and run down the backside of the engine into the drain hole in the frame.     BDC

[pinholenz]

These vent hoses are new to me as well. My bike came without them and to my mind they are unnecessary to the bike's performance. (I am sure they have a function, but I can't think why they need those pipes)

High mileage could mean that the tank is weeping petrol through the seams. Carefully check for any wetness around the edges of the tank on a hot day, especially at the low points where tanks are a bit more prone to rust. Easily fixed with some petrol tank putty. Not pretty, but you will get back on the road until you can do the job when you have time.

There is a tendency on the forum for prophets of doom to predict everything that COULD go wrong in their desire to help diagnose what IS wrong. Don't be despondent! Just work through and test their theories rather than assume the worst. Start with the basics, Fuel and Electrics, then Compression, before you start pulling anything apart.

[Rikugun]

..... to my mind they are unnecessary to the bike's performance. (I am sure they have a function, but I can't think why they need those pipes)

Not that this WILL happen but, under the right circumstances rider and bike moving through the air can cause vortices and low pressure areas that can alter air flow around the carbs. I think one of the reasons they are routed behind the engine is to ensure they are in a relative calm air space. The vents provide atmospheric pressure to the bowls for proper operation.

There is a tendency on the forum for prophets of doom to predict everything that COULD go wrong....... 

Wow, "Prophet of Doom"...That would make an awesome screen name.  :) Is it too late to change mine!?  :P  :laugh: