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Old 02-16-2009, 11:02 PM   #1
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Default ninja jx .21 help plz

hi guys i had a post on here about having troubles with my ninja jx not holding a low idle and raising all the time and every1 figured it was the piston and sleeve worn out though it still has pinch when cold maybe just not enuf when hot so well im going to get it repinched to see if thats the problem as i used a gasket sealer on the bak plate and carb to no avail.

but only other thing i can think of is the piston is it in the right way?
any1 who ownes a ninja will know (if taken it apart) that the piston has one side that comes down longer than the other toward the bottom at one side which i had that part facing the exhaust port just wondering if theres a specific way its ment to face?

could this effect tuning?
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Old 02-16-2009, 11:21 PM   #2
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First off, the most likely problem with and engine slowly increasing rpm while idleing is caused by the idle speed being set to low and the LSN being set to lean to compensate. The engine slowly starts leaning out as it sits. This will hurt the engine....More common, you see the idle speed set to high and the LSN set to rich to compensate. Still for what it's worth a worn P/S or an vacuum leak can cause problems at idle.

Use oxygen sensor safe rtv sealant or one of the specialty products available. Using the wrong type of rtv will cause problems.

The piston skirt is machined to clear the crank in most cases. The backplate is machined to clear the piston on the opposite side. Be sure the con-rod oil hole faces the crank and the the wrist pin clips are fully seated if you need to re-install them. Best to use new clips if possable.
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Old 02-16-2009, 11:32 PM   #3
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The piston skirt faces the exhaust port. Engine should be running a P3 plug. If you blew out a couple of plugs in this engine, you need to take it apart and check for a scored P/S set from the glowplug wire. If so, then it needs to be replaced. If not then try to set the set the carb to:
2-1/4 out on the HSN
Flush 2 o'clock mid-screw
4 turns out on the LSN
Set the idle gap about .8mm-.9mm with reducer out. Adjust the idle screw if needed if it runs. If it still has issues, try a different fuel. Should run, if not check for air leak to the tank or pressure line from pipe or the exhaust itself.
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Old 02-16-2009, 11:45 PM   #4
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That reminds me,,

I have seen a plugged pressure passage on a fuel tank lid cause problems with the mixture leaning out. The engine would rev quite high then die after about 1 minute. Took a while to find the problem. So if that sounds like your problem be sure that the pressure fitting on the pipe, the tubing and, the port in the tank are clear.
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Old 02-17-2009, 02:37 AM   #5
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ezveedub did u say take the reducer out?
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Old 02-17-2009, 03:03 AM   #6
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and guys i have tried everything with this engine tuning wise and it still takes a lil time to come bak to idle after some throttle and if i lower the idle screw when it comes to low idle again it will die so it sounds like a high idle setting when its reving like it is just takes a lil time to reduce until i give it throttle again then off throttle it revs its tits off again like its too lean but richening doesnt help it just makes it come to an idle sooner and makes it stall easier bcuz its too rich.

so to sum it up with a good race tune (not too rich or not too lean) it still revs its tits off after some throttle taking like 15 secs to return to good idle.
and ive had this engine flame on me alot during races when tuned nicely but with the idle high to compensate for flame outs. i just cant use it as it is anymore.

i checked the fuel tank i blew on the pressure line and fuel came out the tank outlet so all is clear and my pipe is clear too.

as i said above ive tried to seal the bakplate and the carby and it seemed like it did the trick all was good but then by the first race finished it was bak doing it again (high idle after throttle taking time to come downto good idle)
so maybe there was a leak and i fixed it but the gasket sealer i used wasnt doing its job after the engine heated up to running temp.

i am going to get the piston and sleeve repinched to see if that helps.
and to find out wheather that is the complete problem if pinching it doesnt help then i know its something else.

so whats the best gasket sealer i can use? i used a high heat resistant one for real cars.
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Old 02-17-2009, 03:04 AM   #7
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Quote:
Originally Posted by downunder23 View Post
ezveedub did u say take the reducer out?
i am sure he means while setting the idle gap and then re-install afterwards. how many gallons do you have on motor and have you ever had it too hot, +235F'ish? check your compression at operating temp. if it feels like no compression, it may be a sign for a needed pinch.
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Old 02-17-2009, 03:37 AM   #8
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also what causes air bubbles in the fuel line?
it seems to me that the engine is leaning out the harder it sucks which the reason its taking so long to go bak to idle cuz its still lean and sucking.
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Old 02-17-2009, 06:08 AM   #9
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I would check your tank lid. whith the car running push down on the tank lid, if you can push it down any, you have a bad seal on the tank. Try this after running a few minutes so that it warms up. Just cause it seems to seal ok when cold, does not mean it will still seal good when warmed up.
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Old 02-17-2009, 07:54 AM   #10
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Quote:
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also what causes air bubbles in the fuel line?
it seems to me that the engine is leaning out the harder it sucks which the reason its taking so long to go bak to idle cuz its still lean and sucking.
Its leaking air. Bubbles are a good clue. You need to find out where the bubbles are coming from. A hole in the fuel line is possable, but most likely it's a problem in the tank. I have seen a few tanks that had a cracked pick-up tube. Usually the engine will run fine until the fuel level drops to a certain point, then you start having problems that get worse as the fuel level drops farther. Tanks with primer pumps can also cause bubbles in the fuel line.

Only other reason for bubbles in the fuel line is fuel foaming. This has not been very common in the last several years because fuel manufacturers have worked on their formulas. Still, a high oil content fuel will tend to foam more.
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Old 02-17-2009, 09:22 AM   #11
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What car is this JX21 in? What fuel is being used?
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Old 02-17-2009, 09:39 AM   #12
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If you are getting air bubbles it is an air leak. Check some of the things others have said. There is no need to get it pinched. That is NOT your problem. I have a v-spec with just about no pinch and it still runs great. You might want to try a new tank and fuel lines. That is an easy and fairly cheap way to insure it is not in the fuel system. It is a good Idea to replace these items fairly often anyway. I would also get some different sealant. I use racers edge carb sealant. If it ran well right after you sealed it up and started running eratically after awhile it is likely that the sealant you used was not fuel safe and dissolved. I would also reccomend setting the carb needles back to factory settings and restart from there. Also change the glowplug to be sure.
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Old 02-17-2009, 01:16 PM   #13
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yeah well the car this jx is in is an xray 808 like 5 meets old
i will check the tank best way to do that is to put it in water and blow on it with fuel line yeah? or if it passes that test doesnt mean to say its right bcuz under pressure it might still have a small hole maybe.

when this first started doing this i did change all the fuel line even the pressure line i have a sneaking suspiscion it may be the fuel filter leaking air.

i wouldnt think just an air leak in the actual engine would cause bubbles in the fuel line would you? provided there are no leaks in the tank or lines as the air is being sucked in from the engine not the fuel or i spose now i think of it maybe due to the engine sucking air (if thats the case) its not sucking hard enough to pull the fuel in hard enuf to not cause bubbles.

i am going to buy this stuff called rtv blue 02 sensor safe silicon sealer.
it was recomended on another thread i saw for this problem to seal up an engine.
so ill try that before i get it pinched.
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Old 02-17-2009, 01:21 PM   #14
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Quote:
Originally Posted by downunder23 View Post
yeah well the car this jx is in is an xray 808 like 5 meets old
i will check the tank best way to do that is to put it in water and blow on it with fuel line yeah? or if it passes that test doesnt mean to say its right bcuz under pressure it might still have a small hole maybe.

when this first started doing this i did change all the fuel line even the pressure line i have a sneaking suspiscion it may be the fuel filter leaking air.

i wouldnt think just an air leak in the actual engine would cause bubbles in the fuel line would you? provided there are no leaks in the tank or lines as the air is being sucked in from the engine not the fuel or i spose now i think of it maybe due to the engine sucking air (if thats the case) its not sucking hard enough to pull the fuel in hard enuf to not cause bubbles.

i am going to buy this stuff called rtv blue 02 sensor safe silicon sealer.
it was recomended on another thread i saw for this problem to seal up an engine.
so ill try that before i get it pinched.
Yeah I can almost guarentee that it is not a compression problem. I would remove the fuel filer and run a straight line. If it is still doing it then, you know it wasn't the filter. if it stops doing it you have found your problem. Fuel filters leak all the time, thats why I don't run them. Your tank has a built in filter. you don't need the inline filter. All they do is boost volume a lil' and cause lots of problems.
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Old 02-17-2009, 02:20 PM   #15
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+1

It's hard to test the tank itself. Best thing is to eliminate any other possabilities first (fuel line, in-line filter) then if you are still getting air bubbles in the line, change out the tank.
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