Is this a compression issue?

[two-fiddy]

I am in the process of resurrecting an 06 250 that was dropped and then left sitting for 2 years. fall was on the right side and seems to have involved significant sliding as the front master cylinder and brake lever are both ground down.

I have done the major points, oil, brake work, carb cleaning, new gas, and other small things I cant think of atm.

Currently the bike will start reliably and stay idled however the right cylinder does not seem to be firing on its own, it seems to start up if I rev to about 3-4k and it will also start if I remove the air box and block the right carb's air intake with my head (forcing a vacuum). however the instant I remove my hand or lower the revs it loses the right cylinder again. I believe it may have a compression issue or need a carb synch, but I would like to get some other opinions as I am a new to bike mechanics and only have so much money to throw at it.

[Motofool]

Welcome, Tyler !!!

It could be several things:
1) Electrical connections to coil and spark plug.
2) Perforated or hard to slide up carb diaphragm.
3) Leaky valves or rings.

[two-fiddy]

Originally Posted by Motofool

Welcome, Tyler !!!

It could be several things:
1) Electrical connections to coil and spark plug.
2) Perforated or hard to slide up carb diaphragm.
3) Leaky valves or rings.

sparks are big, clear, and strong
carb diaphragms are both soft and supple
your third point is intimidating as i have not yet and i hoped to avoid cracking the engine

[jkv45]

My money is on a blockage in the carb. Probably the idle mixture passage or Pilot Jet.

[CaliGrrl]

Welcome! I hope these folks can help you figure out your problem.

[two-fiddy]

Originally Posted by jkv45

My money is on a blockage in the carb. Probably the idle mixture passage or Pilot Jet.

Carbs have been thoroughly cleaned and both main and idle jets are beautifully clean. blasted with carb cleaner and ran guitar string through and through.

[Motofool]

Originally Posted by two-fiddy

sparks are big, clear, and strong
carb diaphragms are both soft and supple
your third point is intimidating as i have not yet and i hoped to avoid cracking the engine

The thing is that sparks can jump big at atmospheric pressure, but not under compression.

If you can, observe if both needles go up together and inmediately as you twist the handle.
Diaphragm could be leaking and would only rise the needle when vacuum gets strong.
It could also have abnormal resistance in its guides or be incorrectly linked to the needle.

For the valves, you don't have to split the engine.
The valves require periodic adjustment of the specified gaps.
A leak down test could tell you if all the valves are closing properly.
A compression test would tell you about the condition of the rings.

[two-fiddy]

Originally Posted by Motofool

The thing is that sparks can jump big at atmospheric pressure, but not under compression.

If you can, observe if both needles go up together and inmediately as you twist the handle.
Diaphragm could be leaking and would only rise the needle when vacuum gets strong.
It could also have abnormal resistance in its guides or be incorrectly linked to the needle.

For the valves, you don't have to split the engine.
The valves require periodic adjustment of the specified gaps.
A leak down test could tell you if all the valves are closing properly.
A compression test would tell you about the condition of the rings.

that makes enough sense, however if i place my hand over the air intake for the right carb the cylinder will come alive almost instanly and run perfectly, so it doesnt seem like spark is an issue, as for the diaphragm, how would i go about observing this while the carb is on the engine? or is this a bench test? also how would i know if it is incorrectly linked to the needle?

thanks for all the help!

[Triple Jim]

I'm with Jay, my money is on a blocked pilot circuit in the right carb too. Not wanting to run unless choked (with your hand) or unless run fast enough to get into the needle jet circuit is exactly what happens if the pilot circuit is clogged.

[two-fiddy]

Originally Posted by Triple Jim

I'm with Jay, my money is on a blocked pilot circuit in the right carb too. Not wanting to run unless choked (with your hand) or unless run fast enough to get into the needle jet circuit is exactly what happens if the pilot circuit is clogged.

i will gladly pull the carb and check again but i know i had it clear and open.
sorry if i sound a bit offended or on edge its just really frustrating to have it so close to right and i cant figure this out!

[two-fiddy]

also what is a good compression tester thats not $100?

[jkv45]

Originally Posted by two-fiddy

Carbs have been thoroughly cleaned and both main and idle jets are beautifully clean. blasted with carb cleaner and ran guitar string through and through.

Well...it still sounds like a carb issue to me...

Something isn't right.

[Ram Jet]

Originally Posted by two-fiddy

i will gladly pull the carb and check again but i know i had it clear and open.
sorry if i sound a bit offended or on edge its just really frustrating to have it so close to right and i cant figure this out!

I'm grasping at straws here. I had a 1973 Kaw 500 H1 triple. It had CDI ignition and an "A" unit and a "B" ignition control module. One controlled high speed spark, 3,000 RPM + and the other low speed. My low speed unit crapped out and I replaced it and the problem was solved. I don't know enough about the Ninja ignition system yet (I just got my 2007 250 on 03/05/17.

Just sittin' here thinkin'.

[verboten1]

it ran, it crashed, it sat. At no point while sitting did the engine wear out.
There is probably a passage that is still plugged in the carb. Did you ultrasonic clean the carb?

Did you pull every jet and screw out?


When you block air, it runs. Fuel and air are handled by the carbs.

[Motofool]

Originally Posted by two-fiddy

that makes enough sense, however if i place my hand over the air intake for the right carb the cylinder will come alive almost instanly and run perfectly, so it doesnt seem like spark is an issue, as for the diaphragm, how would i go about observing this while the carb is on the engine? or is this a bench test? also how would i know if it is incorrectly linked to the needle?

thanks for all the help!

You are welcome

Follow this link and study how these constant velocity carburetors work, modulated by the vacuum of the engine.

https://www.ninjette.org/forums/show...3&postcount=12

That should explain why your hand partially blocking the right inlet makes the proper mix reach the right cylinder.

If you can place a mirror where you can place your hand over the intake, you may be able to see what both slides and needles are doing.
My impression is that the right ones are not responding as quickly and well as the left ones do to the twist of the handle.

It is easy to connect the needle to the slide and spring in the incorrect manner.

Check these ways to test mechanical leaks inductive to low compression:
http://www.dansmc.com/leakdown.htm

http://www.dansmc.com/compression_test.htm

Avoid frustration, be methodical while trying to find the problem.
We can guide you though the troubleshooting process, but cannot replace your eyes and your hands: you will fix the problem.

[two-fiddy]

This has been an awesome place! I love all the information and help guys, thanks! I am going to pull the carb again this afternoon and I will clean it super meticulously. I do not have access to an ultrasonic cleaner. I do have the Clymer's manual and it has been super helpful. I think I can get a mirror in place as the previous owner has done the cut the battery tray away from the airbox to make carb removal a lot easier. should the bike be running when i look at the slides or is off better?