What’s wrong with my bike?

[Kurf]

Trying to find out what the .... is wrong with my bike.

My 7/11 has BST36’s from the 750 engine. Pilot 40, Main 150, mixture 2,5 out and needle in middle clip. Needles seem to be dynojet and are new, just as emulsion tubes. Seemed like a good starting point.

Tried to do a test run today : nice weather and bike starts ok and runs fine on idle.

It picks up good on throttle and runs on all four cilinders.

Riding is a different story : runs rough like on three cilinders and wont go past 4-5000 rpm ; doesn’t pull through....

When warm it cuts out on closing throttle and is difficult to start again.

Is it fuel or electrical?

Any ideas anyone?

 

[Blubber]

First thought is electric...

Had the same symptoms when one  coil packed in.

The coil was cracked and the engine heat made it worse.  I think it was short circuiting internally due to windings touching each other. 

[CockneyRick]

As above, or plugs breaking down when hot, or weak spark caused by coils or plugs  

[Kurf]

Coils are new...

[Kurf]

Thanks for the advice guys ( more suggestions are still welcome)

Next thing : will change sparkplugs and swap cdi with one of my friend’s bike.

To be continued ( soon I hope with some pics of me riding the damn thing...)

[Kurf]

Did not change plugs yet ( will do anyway) but found out following :

Carbs were out of balance : especially #4 was way out. Now sorted and bike no longer runs on three cilinders.

Bike kept revving on idle : false air. Did not think I had to check my new inlet rubbers for leakage but one of them did. Mounted all inlets again with a smear of fluid gasket. 

Bike now starts and runs fine.

Dyno run still to come to get things fine tuned.

Happy sofar...

[no class]

inlets and fluid gaskets ?  How many other " band aids" you have going on hmmm ?  Go get the O rings .....OEM only ..... and the clouds will clear and the sun will shine and the birds will sing

[Kurf]

13 hours ago, no class said:

inlets and fluid gaskets ?  How many other " band aids" you have going on hmmm ?  Go get the O rings .....OEM only ..... and the clouds will clear and the sun will shine and the birds will sing

Inlets are OEM including the o-rings... bought new at cmsnl.... that’s why I’ m surprised one leaked anyway. 

[CockneyRick]

Were the inlet Ally faces clean & not corroded?

[370steve]

On 07/04/2018 at 3:09 PM, Kurf said:

Trying to find out what the .... is wrong with my bike.

 

When warm it cuts out on closing throttle and is difficult to start again.

 

 

usually caused by over rich idle mixture

[Kurf]

9 hours ago, CockneyRick said:

Were the inlet Ally faces clean & not corroded?

Yes sir... and bolts were not loose when I took them off.

[Kurf]

Right then..... been very busy at work and now got chance to try the bike after closing the air leaks.

starts fine : just one push and it fires up but : high revving ( 3000 rpm ) and no go on cilinder 2 and 4..... 

Starting to “dislike” this bike....

Question stays : wtf is wrong ???

[Blubber]

2 and 4? 

That rules out coil and ignition but not spark plugs, sparks boots, high tension leads and sadly also carbs.

 

Assuming you put the right boots on the correct plugs...  Seen That before 

[clivegto]

Swap 2 & 4 plugs round with 1 & 3 then you will know if they are at fault.

[Kurf]

12 hours ago, Blubber said:

2 and 4? 

That rules out coil and ignition but not spark plugs, sparks boots, high tension leads and sadly also carbs.

 

Assuming you put the right boots on the correct plugs...  Seen That before 

Thanks Blubber.

I start to suspect the carbs.... I have a set of 40’s to try but no intake rubbers.

Will first fit four new plugs.

[nlovien]

difficult to follow your path of observations - bit of randomness that in itself is a clue

see when you found the carbs out of sync - adjusted and now have high idle, did you also follow through, confirm the carbs are not hanging on the cables - adjust idle on the throttle stop then fine tune via the idle screw adjusters

when you fitted new coils - did you check the power supply circuit to them to see if you have high resistance / volts drop via a poor connector / switch - or a poor earth

it gets frustrating but when your chasing and replacing, you often have to go back over checks and adjustments and you sometimes need to look at all the bits that connect to the changed ones in order to find the root cause versus chasing the effects

are you getting a consistent and good fuel flow ?

[Kurf]

4 hours ago, nlovien said:

difficult to follow your path of observations - bit of randomness that in itself is a clue

see when you found the carbs out of sync - adjusted and now have high idle, did you also follow through, confirm the carbs are not hanging on the cables - adjust idle on the throttle stop then fine tune via the idle screw adjusters

when you fitted new coils - did you check the power supply circuit to them to see if you have high resistance / volts drop via a poor connector / switch - or a poor earth

it gets frustrating but when your chasing and replacing, you often have to go back over checks and adjustments and you sometimes need to look at all the bits that connect to the changed ones in order to find the root cause versus chasing the effects

are you getting a consistent and good fuel flow ?

Hi Nlovien

Thanks for your reply.

I only had the bike on dyno for very short moment when we discovered the air leak. As soon as there’s more dyno time ( Dyno guy helps me out in spare time) we will investigate further in regards of the idle.

I am no good at all at electrics : got everything cleaned up but do not know how to measure stuff on coils or leads etc.

Fuel flow is ok : alteady swapped taps because previous was no good, even after a rebuild.

That is why I suspect the carbs... Will try my 40mm set ( that recently came off a good running standard 1100 )as soon as I can borrow some inlet rubbers from a mate who has two 1100’s in the shed.

Thanks again, will be continued....

[August17]

Had a problem with my 1200 bandit carbs kept fowling  one plug, worked out in the end the fuel bowl gasket was letting fuel into the motor bypassing the pilot jet, the circular part of the fuel gasket had very fine markings showing were the fuel had been bypassing across it,new gaskets on each carb and it was a goer

[nokturnal]

Dyno jet needles do not work with OEM emulsion tubes and OEM needles don't work with dynojet emulsion tubes.

This is something I have read...

[Kurf]

On 26-5-2018 at 1:41 PM, August17 said:

Had a problem with my 1200 bandit carbs kept fowling  one plug, worked out in the end the fuel bowl gasket was letting fuel into the motor bypassing the pilot jet, the circular part of the fuel gasket had very fine markings showing were the fuel had been bypassing across it,new gaskets on each carb and it was a goer

Hi August17, thanks for the tip : will replace the gaskets just to be sure.

[Kurf]

On 26-5-2018 at 2:10 PM, nokturnal said:

Dyno jet needles do not work with OEM emulsion tubes and OEM needles don't work with dynojet emulsion tubes.

This is something I have read...

Hi Nokturnal : needles and tubes were bought as a set so should work together. Thanks anyway for the tip

[Solcambs]

Are you sure it's running fine when it starts? e.g. here's mine starting for the first time after the rebuild  ...as it fires it sounds OK until you try to rev it. This was running on less than 4 cylinders at the time ...

 

[Kurf]

Update :

At last start up bike ran on 1 and 4 only..

Switched plugs from 1 and 2 and 1 then did not go : foul plug.

Bike runs on 1,2 and 3 : no go on 4 so I switched plugs ( no change ) and then leads from 1-4 ( no change )

Must be a fuel issue :

Carbs are now back from ultrasonic bath and hopefully #4 will work when I put everything back on the bike.

to be continued...

[clivegto]

Does sound like it's the carbs then. Best of luck with it.

[Suban12]

Hopefully carb clean fixes this for you.I presume that you checked valve clearances prior to carb balance?If you are going to the dyno I would make sure engine health is good ie good compression readings on all 4 cylinders,valve  clearances are good and new plugs all around.                                                                                                                                   Did this running problem happen after the bike had sat for a few months or did it get worse as you continued to ride the bike over a period of time?Or are these carbs new to the bike?