vfr nc21

[kiwi cowboy]

ok people i ust bought a vfr400 with a nc21 motor.
now the thing is it seams to run fine but it does seem to surge a little at idle and seems to me to lack power at crusing speed the guy i got it off sent me wot he told me were the main jets from oridginal carbs witch are112 size[inside hole dimencions i assume] and the ones in it are 110 size will yhis be the reason for the above problem.
has anyone got a manual for a vfr400k 1987 year cheers for any help

[limbimtimwim]

Check the carbs are correctly in their rubber boots. This is easy to fuck up on these engines, it's really hard to see the front right cylinder carb-boot too. If you are feeling gutsy, you can clean the carbs. Change the air filter. Check and clean and gap the spark plugs. Make a note if one of them looks dramatically different from the rest.

Don't bother thinking about idle stability unless the engine is proper warm, my NC35 is a crabby old bitch until it is warmed up, then it is a peach. Perhaps your idle speed is too low? Is it at least 1500rpm when fully warm?

You are correct, the number refers to the size a hole. You can obtain Keihin main jets without too much difficulty, however the minor change in main jets won't have changed the idle characteristics. Someone has tried to make it go faster by making the engine a little leaner by putting in the smaller mains, perhaps they borked the carbs while they were in there?

There is a Haynes manual for the NC30 and NC35. That should be close.

[kiwi cowboy]

Check the carbs are correctly in their rubber boots. This is easy to fuck up on these engines, it's really hard to see the front right cylinder carb-boot too. If you are feeling gutsy, you can clean the carbs. Change the air filter. Check and clean and gap the spark plugs. Make a note if one of them looks dramatically different from the rest.

Don't bother thinking about idle stability unless the engine is proper warm, my NC35 is a crabby old bitch until it is warmed up, then it is a peach. Perhaps your idle speed is too low? Is it at least 1500rpm when fully warm?

You are correct, the number refers to the size a hole. You can obtain Keihin main jets without too much difficulty, however the minor change in main jets won't have changed the idle characteristics. Someone has tried to make it go faster by making the engine a little leaner by putting in the smaller mains, perhaps they borked the carbs while they were in there?

There is a Haynes manual for the NC30 and NC35. That should be close.

cheers for that but wot is borked ? and am i better to put the 112s back in or is it not worth the trouble.it does pick up ok from 1ooks or so if i drop a cople of geers so it maybe ust me after riding a 750. im realy comparing it to a gsx400 impulse i used to have powerwise.