Jump to content

Carb balancing and tuning


splke

Recommended Posts

Johnnie Mototrans

That might be a clue Neil.

Coils on their way out can run fine on a cold engine then go haywire when things get hot.

Have a look at the spark plugs to see if one is different to the others.

That might not tell you what the problem is but it could tie it down to one cylinder.

Swap the coils and see if the problem moves too.

With other electronics heat opens up the invisible crack in the circuit and all the electricity falls out. Or something like that.

Identifying a dud electrical component is often just a matter of trial and error but immensely satisfying when you do find it.

However, we are getting way out of my area of competence so you might want a second opinion.

 

 

  • Like 2
Link to post
kayz1

Early bikes had lots of problems with the plug leads...

  • Like 1
  • Thanks 1
Link to post
splke

I have a spare set of Coils we decided not to install as old looked fine I will swap them over  and see if it helps 

Thank you 

  • Like 1
  • Haha 1
Link to post
MatBin
9 hours ago, Johnnie Mototrans said:

That might be a clue Neil.

Coils on their way out can run fine on a cold engine then go haywire when things get hot.

With other electronics heat opens up the invisible crack in the circuit and all the electricity falls out. Or something like that.

Had exactly that on a BM years ago, soon as things got warm the outer casing on the coils expanded and the leccy tracked away rather than go down the plug leads.

  • Like 1
Link to post
Tex
9 hours ago, splke said:

I have a spare set of Coils we decided not to install as old looked fine I will swap them over  and see if it helps 

Thank you 


Dude, I wish I had £1 for every time I replaced something that ‘looked fine’.. ;) 

The workshop manual will tell you that test procedure for both primary and secondary resistance. 

  • Like 3
Link to post
Andy m

I assume we've tried squirting WD-40 over the carb rubbers to check for air leaks? You'd expect this to be more random, becoming permanent later, but it's an easy one to discount. 

 

Andy

Link to post
splke
25 minutes ago, Andy m said:

I assume we've tried squirting WD-40 over the carb rubbers to check for air leaks? You'd expect this to be more random, becoming permanent later, but it's an easy one to discount. 

 

Andy

i havent no , its funny as someone on bandit forum is convinced its an air leak somewhere 

the carbs have had a refurb kit last week could this still be leaking ? any tips on how to implement this test andy ? it is pretty tight in there :(

 

Link to post
Andy m

Easy test, just get it misbehaving then start spraying bit by bit. Round the manifold rubbers, carb tops, any vacuum pipes etc. All that will happen is that the WD-40 will seal the leak and it'll behave until the oil is sucked in or evaporated. You are looking for misassembly or cracks/dings not spotted during the rebuild. If the WD-40 just sits there with no reaction on the rev counter the problem is elsewhere. 

 

Not sure how many carbs you have or which cylinders they feed, but on the CL I seem to spend a lot of time with one plug off and sparking into an open hole during such diagnosis. The idle drops running on one pot, but when one side reacts differently you halve the search area. 

 

Andy

Edited by Andy m
  • Like 1
Link to post
ChrisCB

Just had a read through this thread and something to check.

 

What spark plugs are fitted? If it has "R" resister type Bandits really don't idle well with them as the spark is very weak especially if coupled to resister type plug caps.

Link to post
  • 2 weeks later...
splke

update 

ive swapped out the coils for new (non OEM)

idle speed is still all over place 

will try the wd40 test just difficult with tank on and pipes are very short 

might buy a non oem petcock just to rule that out too.

 

On 01/07/2021 at 09:53, Chris750 said:

Just had a read through this thread and something to check.

 

What spark plugs are fitted? If it has "R" resister type Bandits really don't idle well with them as the spark is very weak especially if coupled to resister type plug caps.

fitted these NGK CR9EK plugs: https://www.amazon.co.uk/gp/product/B000CSEZ42/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

Link to post
Trev
59 minutes ago, splke said:

update 

ive swapped out the coils for new (non OEM)

idle speed is still all over place 

will try the wd40 test just difficult with tank on and pipes are very short 

might buy a non oem petcock just to rule that out too.

 

fitted these NGK CR9EK plugs: https://www.amazon.co.uk/gp/product/B000CSEZ42/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

I've got one of these which comes in handy 

https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwjBxp7zluLxAhXS7e0KHQ1nBlMYABAFGgJkZw&ae=2&ohost=www.google.com&cid=CAESQeD28zWvUQkwM0ZMsXP2rn3647uRVt5Tg4Li4gJlbGaRp5nLSchlAjTU3DRFnVAML67TPoM4wWPqvpMh5ustXYE1&sig=AOD64_3GSCCbGZq807VtMuvY87hQNT0v-g&ctype=70&q=&ved=2ahUKEwiT7pTzluLxAhUfEWMBHXSCCO4Qwg96BAgIEA8&adurl=

Link to post
splke
Trev
1 hour ago, splke said:

looks good thank you no issue with not having the vacuum connected ?

I've used it on a CV carbed XS 650 OK but not sure that means it will work on others, it has an on/off tap so flow can be crudely controlled

  • Like 1
Link to post
splke

i know summat i wish id never bothered trying to restore it the bloody thing

 

  • Haha 1
Link to post
Trev
1 hour ago, splke said:

i know summat i wish id never bothered trying to restore it the bloody thing

 

 

..... and there endeth the lesson for all us garage tinkerers and home restorers :D

  • Haha 2
Link to post
  • 2 weeks later...
splke

Well at last an update

coils made no difference neither did the plugs 

so i decided to remove the PAIRs system as it is only there for emmisions and is silly heavy and really not required 

while doing this i found that some doylem had attached carb 3 vacuum pipe to the tank breather t piece rather than the pairs valve :doh:

 

So it is now running reasonably well well actually its flipping brill apart from a but rough on idle 

 

happy days

 

thank you all for your input

  • Like 3
Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...