Bike running rough / surging when opening throttle

StewMcGrew

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I've had the throttle bodies disconnected ( I didn't disconnect the cables) when I took the bike apart to get the rear sub frame powder coated. On putting it back together and when starting, it is now running rough and sounds like misfires, poor revving on from idle, but once upto 5k it's smoother but still rough.

I think the throttle bodies are out of balance but not sure. I've had a look on amazon for a balancer but all seems to be chinese stuff with no reviews.

Can anyone recommend a decent one that they've used in the past that won't break the bank?

Thanks
 
This is the one I use and never had any problems
http://www.carbtune.co.uk/
I use it and I have no connection to the company

Just a thought but are the covers still on the vacuum plugs as they might have popped off when you removed and refitted the throttle bodies
 
waggy said:
This is the one I use and never had any problems
http://www.carbtune.co.uk/
I use it and I have no connection to the company

Just a thought but are the covers still on the vacuum plugs as they might have popped off when you removed and refitted the throttle bodies
Click to expand...

I will have to double check - I know that the right hand one still has it on.
 
Also check that the outer throttle cables are seated properly at both ends, so that the butterfly`s both are shutting.
 
Sounds like one or both of your throttle outer cables are unseated, usually at the junction box end.
 
StewMcGrew said:
I've had the throttle bodies disconnected ( I didn't disconnect the cables) when I took the bike apart to get the rear sub frame powder coated. On putting it back together and when starting, it is now running rough and sounds like misfires, poor revving on from idle, but once upto 5k it's smoother but still rough.

I think the throttle bodies are out of balance but not sure. I've had a look on amazon for a balancer but all seems to be chinese stuff with no reviews.

Can anyone recommend a decent one that they've used in the past that won't break the bank?

Thanks
Click to expand...

The most accurate balancer is possible to 'build' your self.

A bit cumbersome explanation, but bear with me...

Go to your hardware store or wherever they sell lengths of clear tubes. Go for two dimensions. The smallest tube should have an inner diameter of 4 mm (to fit the outlets on the bike). This is the one that is pushed into your vacuum outlets on the bike. The other dimension will have an inner diameter that matches the outer diameter of the thinner one. In my case the larger one was 6 mm inner diameter

'Building':

The goal is to allow the larger tube to hang down from your ceiling in a U shape, and you fill it with two-stroke oil (it's colored and if you screw up it's made to handle being sucked into the engine.)

Allow the larger tube to be apprx. 5 meters, This allow for the U to be 2 m tall and then 0,5 m at each end where you connect the smaller tubes. The smaller tubes are connected to the larger tubes, and (at least in my case) I just pushed one into the other, no need for any type of glue. The other end of the small tubes are put onto the vacuum outlet on your engine. In my case I used 2 x 3,5 m of length of the smaller ones.

The point is: You now have one long tube, larger diameter in the middle and with two smaler tubes, one at each end.

Allowing the center section to hang down from your ceiling in a U - shape, and you find some means to keep the two lengths hanging down close to each other will allow the oil inside the large tube to have the same level in both 'legs'.

As each 'leg' is connected to one of the cylinders, any time there is a slight difference in vacuum between the cylinders, this will immediately show on the oil level between the 'legs'. I allowed the level to start at the middle of the tube, allowing for +/- 80cm of level change. That was plenty.

Is it accurate? You bet. I built one in order to sync. the carbs on my 90S. You could barely touch the adjustment screw and it would show.

It is my humble opinion that you are not able to get a more accurate way of sync. the cylinders, and the total cost was less than £20.

A but cumbersome to rig, but once I was done with it I coiled the tubes for storage, with the oil inside, then I connected the two open tube ends with a leftover from the larger tube to seal it off.
(and you will be in trouble if you want to test the bike on the road while performing the sync :D )
 
StewMcGrew said:
Fuck! that's tank off if it's the case!
Click to expand...

Not necessarily. Twist and hold throttle firmly on. As you’re holding it, with the other hand pull/push and move around the throttle cable at the throttle body, first one side then the other, this usually causes the outer cable/covering to pop back into the junction box ..... that is of course if it’s the problem in the first place :D Good luck
 
Steptoe said:
Not necessarily. Twist and hold throttle firmly on. As you’re holding it, with the other hand pull/push and move around the throttle cable at the throttle body, first one side then the other, this usually causes the outer cable/covering to pop back into the junction box ..... that is of course if it’s the problem in the first place :D Good luck
Click to expand...

Thanks
 
StewMcGrew said:
Fuck! that's tank off if it's the case!
Click to expand...
If you've had the rear subframe off, tank-off is nothing! It's easier than the 1150, but takes way longer just because of all the flippin screws. But at least it's not an RT

ps. Good luck. Hopefully it's a straightforward fix - sounds like it will be


Sent from my SM-G975F using Tapatalk
 
knutk said:
The most accurate balancer is possible to 'build' your self.

A bit cumbersome explanation, but bear with me...

Go to your hardware store or wherever they sell lengths of clear tubes. Go for two dimensions. The smallest tube should have an inner diameter of 4 mm (to fit the outlets on the bike). This is the one that is pushed into your vacuum outlets on the bike. The other dimension will have an inner diameter that matches the outer diameter of the thinner one. In my case the larger one was 6 mm inner diameter

'Building':

The goal is to allow the larger tube to hang down from your ceiling in a U shape, and you fill it with two-stroke oil (it's colored and if you screw up it's made to handle being sucked into the engine.)

Allow the larger tube to be apprx. 5 meters, This allow for the U to be 2 m tall and then 0,5 m at each end where you connect the smaller tubes. The smaller tubes are connected to the larger tubes, and (at least in my case) I just pushed one into the other, no need for any type of glue. The other end of the small tubes are put onto the vacuum outlet on your engine. In my case I used 2 x 3,5 m of length of the smaller ones.

The point is: You now have one long tube, larger diameter in the middle and with two smaler tubes, one at each end.

Allowing the center section to hang down from your ceiling in a U - shape, and you find some means to keep the two lengths hanging down close to each other will allow the oil inside the large tube to have the same level in both 'legs'.

As each 'leg' is connected to one of the cylinders, any time there is a slight difference in vacuum between the cylinders, this will immediately show on the oil level between the 'legs'. I allowed the level to start at the middle of the tube, allowing for +/- 80cm of level change. That was plenty.

Is it accurate? You bet. I built one in order to sync. the carbs on my 90S. You could barely touch the adjustment screw and it would show.

It is my humble opinion that you are not able to get a more accurate way of sync. the cylinders, and the total cost was less than £20.

A but cumbersome to rig, but once I was done with it I coiled the tubes for storage, with the oil inside, then I connected the two open tube ends with a leftover from the larger tube to seal it off.
(and you will be in trouble if you want to test the bike on the road while performing the sync :D )
Click to expand...

Have read somewhere else about a method like this but the tubes were fixed to a plank of wood. Any issues you can see with that? I’m guessing the set up is like an M shape with the feet of the M being the connection to the vacuum inlets. Presumably quite tricky to stop the oil running into the engine when setting it up. Does sound accurate mind you. Did you notice an improvement in smoothness ?
 
Steptoe said:
Not necessarily. Twist and hold throttle firmly on. As you’re holding it, with the other hand pull/push and move around the throttle cable at the throttle body, first one side then the other, this usually causes the outer cable/covering to pop back into the junction box ..... that is of course if it’s the problem in the first place :D Good luck
Click to expand...

That sorted it out!

Thanks
 
davnjud said:
Have read somewhere else about a method like this but the tubes were fixed to a plank of wood. Any issues you can see with that?
Click to expand...

I think that fixing to a plank will be just fine.

My reason for allowing the tubes to hang down by gravity only was the consideration for storing afterwards, as I can coil the tubes for easy storage,
And gravity will keep them down (using a rather soft type of tubes)

davnjud said:
I’m guessing the set up is like an M shape with the feet of the M being the connection to the vacuum inlets. Presumably quite tricky to stop the oil running into the engine when setting it up. Does sound accurate mind you. Did you notice an improvement in smoothness ?
Click to expand...

You got it :thumby:, the oil filling the lower center of the M.
The oil quantity used was such that the oil reached up to apprx. half the height to the top. Mounting it I started with the oil -filled center section to hang down first, and then I stretched the tubes from the top and on to the bike.

No oil running into the engine.
 
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