426 trouble

[ex_freestyle]

ok well you see i have just re-built my 400 to a 426 now and it is acting funny on me in the top end i have a stage 1 hotm cam, 4 degree timing key and a 13:1 JE piston in her curtis sparks x-6 full system, no air box lid or snorkle, k and n air filter and cdi and rectifire in it and i got it running today and when its cold i can go pretty good with out opening it up but when it gets hot and im in 4th gear and crack it you can hear the vaulves slaping around and same in 5th but when i idle half pinned it dont do nothing its just when i get on the trottle in 4th and 5th they slap hard and i ajusted my vaulves to what they are supposto be and its jetted to a 190 and its on the 3rd clip on the needle i want to get this thing running right before i go to bruel this weekend so could someone give me some sort of idea what it might be

thanks

[STEVENJANNA]

I can tell you what you're hearing but not why, because I'm working on the same problem on a similar setup. You're hearing what's known as valve ping. It's caused by the pre-detonation of fuel in the combustion chamber. Since you have a 13:1 compression ratio you may need to run a higher octane fuel. The quad I'm dealing with only has an 11:1 JE in it and we have exactly the same issue.

John the IM still doesn't work right.

[davetheslave]

yeah detonation. I have 12.5:1 440, and my motor pings if I run anything less than 106 octane.

[davetheslave]

one more thing: If your running too lean with high octane it will also detonate. So make sure its getting enough fuel, and the octane you run is high

[m36indiana]

i have a 426 with a stg 2 hot cam that runs just fine, i would get rid of the timing degree key heard it wasnt good for a built motor

[GOTFEAR]

Remove your 4deg advance key and use race gas 101 oct or more you dont need that advance key with the compression your runing will run hotter to good luck.

[REDRIDDER]

This info is right from here at atv riders.com"Please note that Curtis Sparks does not recommend this on modified motors due to the extra heat it will generate, so only run this on stock motors. "

[400exrider707]

Ok first things first... some corrective information... pre-ignition and detonation are two completely different things... Lets set it straight before you guys give GPracer2500 an ulcer...

Here is some info he originally posted that will be very useful.


Originally posted by GPracer2500
Detonation and Pre-ignition are two completely different things, what can make things confusing is that one can lead to another and both can occur at the same time. But one doesn't always lead to another and they don't always occur at the same time.

Deto always occurs after the air fuel mixture is ignited and has begun to burn. This ignition source is usually/normally the spark plug firing. The plug fires, the mixture begins to burn, but before the mixture at the edges of the combustion chamber has a chance to burn (if conditions are just right) it explodes violently instead of burning. That is detonation--when some of the a/f mixture explodes rather than burns. Burning (deflagration) and exploding (detonation) are not the same thing.

Pre-ignition is simply when the a/f mixture is ignited and begins to burn (deflagrate) well before the spark plug fires. Deflagration is usually a normal occurance. But what makes it abnormal in the case of pre-ignition is that it's happening at the wrong time.

Deto is the wrong kind of combustion (deflagration is the good kind, detonation is the bad kind). With pre-ignition it is the right kind of combustion but it happens at the wrong time.

Most engines can withstand a certain amount of mild detonation without sudden, catostrophic damage. Deto also usually provides an audible warning that it is happening. Pre-ignition can destroy an engine in a second or two. I'm not aware of an engine that can withstand a continuous pre-ignition condition for any period of time. Deto is somewhat common while pre-ignition is comparatively rare.

Hope that helps some....


more...



Originally posted by GPracer2500
Detonation is caused by some combination of too low a grade fuel, too much dynamic compression, too much ignition advance, and too much heat. Lean air/fuel mixtures can also be a contributing factor and there could be other factors I'm not thinking of at the moment.

Pre-ignition is caused by the creation of an ignition source in the combustion chamber other than the normal firing of the spark plug. High octane fuel only indirectly helps prevent pre-ignition. High octane fuel can help stop deto and deto can cause the hot spot that allows a pre-ign condition to start.....



Now, as far as your problems... what fuel are you running and what are your jetting specs right now? I would definitely lose the timing key, way too much heat. chances are the aluminum cylinder is going to break down and the studs are going to pull. I would have put them in already if you haven't done so yet, regardless if its running "good" Although static compression doesn't really tell you anything, it is a safety rule of thumb that anything 12:1 and higher on these motors should have a heavy duty rod and heavy duty head studs.

[johnsls]

I'm having a simular problem except I notice the noise/valves tapping while riding on the track,, 2nd & 3rd gear,,coming out of turns or climbing.

I can definately say that I hear the tapping more when the bike is heated up or when I've been riding awhile.

I have the 426 11:1 piston kit and run 94 octane.

Can't recall what my jets are. (Steve if you out there see if you rememeber)

[400exrider707]

Originally posted by johnsls
I'm having a simular problem except I notice the noise/valves tapping while riding on the track,, 2nd & 3rd gear,,coming out of turns or climbing.

I can definately say that I hear the tapping more when the bike is heated up or when I've been riding awhile.

I have the 426 11:1 piston kit and run 94 octane.

Can't recall what my jets are. (Steve if you out there see if you rememeber)


Its the hotcam... quite normal

[johnsls]

Originally posted by 400exrider707
Its the hotcam... quite normal

Are you sure??:confused: It only recently started to make noise and I've had it in for over a year. LMK

[400exrider707]

Originally posted by johnsls
Are you sure??:confused: It only recently started to make noise and I've had it in for over a year. LMK


well it was more notorious with the stage I, if it just started you might want to adjust your valves if you haven't already done so.

[1965 honda]

the ping is not normal, i had installed a stage 2 hot cam it made no noise for the first 80 miles. but than it started pinging really bad so i readjusted my valves to .005 intake .006 exhaust no more ping, my motor is very quite now.:macho

[johnsls]

Valves had been adjusted about a few months ago, I've only been out riding about 6 times.. It seems odd the valves would need adjusting again.

BUT we will recheck them.

I kinda thought is had more to do with - the pre-detonation of fuel in the combustion chamber.

[1965 honda]

Originally posted by johnsls
Valves had been adjusted about a few months ago, I've only been out riding about 6 times.. It seems odd the valves would need adjusting again.

BUT we will recheck them.

I kinda thought is had more to do with - the pre-detonation of fuel in the combustion chamber.
i have to readjust every 200 miles. it sucks but all well thats what i get for hopping up the motor:(

[STEVENJANNA]

Originally posted by 400exrider707
Its the hotcam... quite normal

WOW!!!!!:eek2:

[400exrider707]

Obviously none of you have ever used a stage 1 hotcam. It is quite common, not so much with the stage II's, but the stage I's are notorious for it. Search it. I could not get the tick to go away, which in fact got louder as it warmed up. I even went as far as .003intake and .004 exhaust... still ticked so I put it back to hotcams settings, and even then I left them a hair tight. Once I switched to a good synthetic it quieted up substantially but still sounded terrible.

[400exrider707]

Originally posted by 1965 honda
i have to readjust every 200 miles. it sucks but all well thats what i get for hopping up the motor:(


that seems like a long time. I did mine every 2 months which worked out to about 15-20 hours.

[STEVENJANNA]

Originally posted by 400exrider707
Obviously none of you have ever used a stage 1 hotcam. It is quite common, not so much with the stage II's, but the stage I's are notorious for it. Search it. I could not get the tick to go away, which in fact got louder as it warmed up. I even went as far as .003intake and .004 exhaust... still ticked so I put it back to hotcams settings, and even then I left them a hair tight. Once I switched to a good synthetic it quieted up substantially but still sounded terrible.
May I remind you that we aren't talking about a valve tick here, but a pre-det. noise.

[xc_racer1]

Originally posted by ex_freestyle
ok well you see i have just re-built my 400 to a 426 now and it is acting funny on me in the top end i have a stage 1 hotm cam, 4 degree timing key and a 13:1 JE piston in her curtis sparks x-6 full system, no air box lid or snorkle, k and n air filter and cdi and rectifire in it and i got it running today and when its cold i can go pretty good with out opening it up but when it gets hot and im in 4th gear and crack it you can hear the vaulves slaping around and same in 5th but when i idle half pinned it dont do nothing its just when i get on the trottle in 4th and 5th they slap hard and i ajusted my vaulves to what they are supposto be and its jetted to a 190 and its on the 3rd clip on the needle i want to get this thing running right before i go to bruel this weekend so could someone give me some sort of idea what it might be

thanks


with a 13:1 ud have to run race gas. most 400s valves make noise but idk y it would be making that much.

[1965 honda]

Originally posted by 400exrider707
that seems like a long time. I did mine every 2 months which worked out to about 15-20 hours.
i ride 80 to 150 miles per weekend. roughly 10 hours.:ermm: