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Old 11-13-2006, 01:05 AM   #1
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Default 21 vspec problem

hi,

my vspec is behaving badly. it backfires when i start to accelerate past 1/2 throttle(mainly during the first few accel attempts after startup, or after a long period of only low throttle application, like in the tight and twisty stuff and then i go to accel onto the main straight) it almost seems as though its being starved of fuel?

sometimes it'll clear itself out and go fine there after, or else it will bog right down and i have to let up on the throttle to stop it dying, sometimes unsuccessfully. and it will randomly shut down when i get on the gas for a jump/ short straight. it also seems to have a lean bog just enough to hear it and feel it hesitating.

i have tried all number of needle settings and the only difference i get is that the high end adjustments have their respective affects, as you would expect. nothing i do to the low end needle affects the low range, except i can make it too lean, never rich enough though.

i have already checked compression(v good) backplate seal(fine) fuel tubing(no difference after replacing) fuel filter(fine) carby seal(fine), engine head is on tight and secure.

does anybody have an idea as to what my problem may be. i run 20% nitro and i use the head shim. it runs at around 230-260 so no dramas with the temps either.

thanks.
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Old 11-13-2006, 01:17 AM   #2
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simonr23:

You failed to say how much fuel is thru the engine but I would bet its the rear bearing. Get yourself a new TKO ceramic bearing and I bet your problems go away.

I'm curious tho, can you please explain your complete engine break in method to a T. I've got a Vspec in my truggy and it is off the wall performance wise and milage wise. I'm willing to bey your break in/ heat cycle method did the rear bearing in. You can PM me if you wish.

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Old 11-13-2006, 01:32 AM   #3
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sounds like a glow plug to me....

or you are too rich on a needle and to lean on the other...
also check your carb for air leaks
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Old 11-13-2006, 03:49 AM   #4
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You have checked all the odvious except one ! The front bearing seals ! These little rascals will give more grief in the tuning that you can imagine !
Also glowplug ? Are you running a hot one ?
When checking the rear AND front engine bearings make sure there is no lateral play AT ALL ! Also OS has very good bearing fit and you should not be able to slide the crank in and out very easy , if it does your bearings are bad.
When you remove the crankshaft you need to look around the inside race on the front bearing and if you see even the slightest bit of light .... the seals are gone and this will cause incredible incredible tuning troubles ! SO CHECK IT !
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Old 11-13-2006, 04:28 AM   #5
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fuel is about 6ltrs. bearings are standard. i'm 99% sure the rear bearing is fine as there isnt a leak from the backplate at all, which iassume would happen once the bearing stops sealing.
i used a heat cycle method at the default needle settings. gentle running on bitumen for about 3 mins at 200ish degrees farenheit(sp) then stop, put piston at bottom of stroke, let cool to about 85 was 65 ambient at the time. did this 5 times. then did 3x 5mins at same needl settings same cool down, but with a bit more throttle, temps got to about 220. then i started going fairly hard, but still with the stock needle settings for a few more tanks of fuel. finally i went as hard as those rich settings would allow for another few tanks, and then i started leanin the HSN in 1hour increments till i got to about 2.5turns i left the LSN as it was (flush) as the engin still seemed lean down low, in fact i even tried making it richer, but this just caused it to not idle.

i changed the glowplug after break-in but not since the last few tanks where its been playing up.i figured that becauseits idling fine and when it runs well, it is running really well, that wouldnt be the problem.

i think i'll just go ahead and change the bearings over, hopefully they're the problem, im in australia, so will any engine bearings be ok. on these forums there are about 5 brands that people are saying are the best, i'm thinking its just personal preference. and availability. what sorta price can i expect for both bearings?

i use the P3 plug.
cheers.
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Old 11-13-2006, 06:02 AM   #6
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Fast engine for sure
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Old 11-13-2006, 06:32 AM   #7
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Simon before you tear it down again put in a new P3 glow plug, get it warmed up as best possible and let it idle in the car. Shoot some motor spray carefully around the carb base and see if the idle changes. Use very small bursts with the long red extention tube. Don't get it on or around your air filter. If nothing happens around the carb base try the same thing around the front of the crankcase behind the flywheel. Those 2 checks will determine is you have a leak at the carb or a bad front bearing seal. If they both check out OK tear it down. Inspect the crankcase for a hairline crack. (it happens) Take the crank out of the car a reach in with your finger and turn the rear bearing, you'll feel it if it's bad. IF it is rough at all or you see pitting on the balls (thats a bad visual ) the rear bearing is toast.

If it needs replaced get a TKO ceramic from here in the States. I believe TKO will ship worldwide. If you need there website I can get it later but a google search will find it quick I'm sure.
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Old 11-14-2006, 02:58 PM   #8
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TKO ships worldwide www.tkocompetitionedev.com
Thanks Randy!
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Old 11-14-2006, 03:01 PM   #9
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sorry...www.tkocompetitiondev.com/shop/
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Old 11-15-2006, 12:31 AM   #10
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thanks heaps for your responses guys. i replaced the front bearing as the outside of it had lots of fresh oil on it....
the rear bearing had a tiiiiiiny bit of lateral play in it when i put my finger in the 14mm hole and then rocked the outside of the bearing gently back and forward. but the guys at one of our biggest bearing places said it was still fine. ive put i back together and will have give it a good testdrive tomorrow.
cheers.
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