ninjette.org - View Single Post - Pulling the carbs and doing a valve check.

Bob KellyIII · May 9th, 2023, 01:38 PM

Ok I appreciate that approach... but my question is has anyone ever had to use 3 shims under the needles ? I've never heard of that.
...
I would think NO because 2 is alot.... has anyone ever used 3 shims ?
I don't know if they would even fit.... I've never shimmed needles before.
even with re boring and polishing and porting.... I've never had to shim needles before.
.....
I'm thinking maybe sense it is better, just not right yet that something else is causing this problem, what that COULD be escapes me ! if it were a point's system there would be a few things I could try, but the timing is fixed on this thing so it can't be ignition.... the ignition USUALLY works or it doesn't...
but it could be possible that a coil is breaking down at that RPM and causing the flat spot.... just like a sparkplug might do.... but that is Highly unlikely
....
I just thought of a test I could do to see if it is the coils breaking down
sense I have it running on a aux gas tank so the tank isn't in the way.... start the bike up and turn off the lights in the shop and see if I can see any arcing
going on anywhere.... although I have seen coils go bad without any outward signs like arcing.... but usually they fail to work entirely
... come to think of it I did have to take off the coil on the right side.....
...
I am more apt to remove the shims completely and see how it runs then
....that should tell me something if it runs worse then the mid range is probably way too lean because the shims should richen up that area. as well as top end obviously....
but it runs fantastically above 7k or 8k RPM .... and it did before too
it was the bottom end that it barely ran at all at.
.....
I find this whole thing bazar carbs are not that difficult and usually there is no real reason to modify them but that is totally dependent on the machine
some need modified straight off the showroom floor the Yamaha 175 was one
I can remember.... ride it hard and you will fry the piston. they put in too small of a main jet.... Kawasaki 175's were the same way in fact I had a skoal can full of all the main jets I removed to replace with bigger ones...
the DT1 250 Yamaha was one you really had to watch close, they would melt a piston faster than you could blink if their air cleaner came loose or some one changed the filter for a green weeny...
but I do not know about the Ninja 250 at all.... I have no experience with it other than what I have seen here.... it is a bitch to work on that I know from experience. it USUALLY starts easy and runs fine.... why adjusting the valves and having the carbs cleaned changed that makes no sense....
.....
if plug color is any indication of how it was running it was running too rich
so we put smaller main jets in it.... that should NOT change anything else
it should not put a flat spot in mid range.... so what else changed ?
.....it could be that smaller main jets make it run too lean in mid range
(if so the carbs are ****** carbs!) but that is possible... so 2 shims are needed to correct that.... so the bike should be running perfectly right now
.... but it is not.
I don't know.... I have no answers !
....
Bob.....

May 9th, 2023, 01:38 PM	#87
Bob KellyIII Retired motorcycle Mc. Name: Robert Location: Weed, California. Join Date: Jul 2021 Motorcycle(s): 2012 Kawasaki Ninja 250R, 2021 CSC TT250, 1977 Triumph Bonneville 750cc,2001 Honda XR650L. Posts: A lot.	Ok I appreciate that approach... but my question is has anyone ever had to use 3 shims under the needles ? I've never heard of that. ... I would think NO because 2 is alot.... has anyone ever used 3 shims ? I don't know if they would even fit.... I've never shimmed needles before. even with re boring and polishing and porting.... I've never had to shim needles before. ..... I'm thinking maybe sense it is better, just not right yet that something else is causing this problem, what that COULD be escapes me ! if it were a point's system there would be a few things I could try, but the timing is fixed on this thing so it can't be ignition.... the ignition USUALLY works or it doesn't... but it could be possible that a coil is breaking down at that RPM and causing the flat spot.... just like a sparkplug might do.... but that is Highly unlikely .... I just thought of a test I could do to see if it is the coils breaking down sense I have it running on a aux gas tank so the tank isn't in the way.... start the bike up and turn off the lights in the shop and see if I can see any arcing going on anywhere.... although I have seen coils go bad without any outward signs like arcing.... but usually they fail to work entirely ... come to think of it I did have to take off the coil on the right side..... ... I am more apt to remove the shims completely and see how it runs then ....that should tell me something if it runs worse then the mid range is probably way too lean because the shims should richen up that area. as well as top end obviously.... but it runs fantastically above 7k or 8k RPM .... and it did before too it was the bottom end that it barely ran at all at. ..... I find this whole thing bazar carbs are not that difficult and usually there is no real reason to modify them but that is totally dependent on the machine some need modified straight off the showroom floor the Yamaha 175 was one I can remember.... ride it hard and you will fry the piston. they put in too small of a main jet.... Kawasaki 175's were the same way in fact I had a skoal can full of all the main jets I removed to replace with bigger ones... the DT1 250 Yamaha was one you really had to watch close, they would melt a piston faster than you could blink if their air cleaner came loose or some one changed the filter for a green weeny... but I do not know about the Ninja 250 at all.... I have no experience with it other than what I have seen here.... it is a bitch to work on that I know from experience. it USUALLY starts easy and runs fine.... why adjusting the valves and having the carbs cleaned changed that makes no sense.... ..... if plug color is any indication of how it was running it was running too rich so we put smaller main jets in it.... that should NOT change anything else it should not put a flat spot in mid range.... so what else changed ? .....it could be that smaller main jets make it run too lean in mid range (if so the carbs are ****** carbs!) but that is possible... so 2 shims are needed to correct that.... so the bike should be running perfectly right now .... but it is not. I don't know.... I have no answers ! .... Bob..... __________________________________________________ Its too late when you've gone too far !