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Carb Tuning ZR800

2K views 14 replies 7 participants last post by  Cats4Life 
#1 ·
Ok, I pulled the plugs today and got to looking at them and they seemed very good, dark tan. Then I noticed a couple tiny white spots on the electrode, so I tried looking down the plug hole to see if I could see the piston wash, not the best way. I could not see enough of the piston to tell what was happening, but I did notice a very clean spot right in the middle of the piston right where the plug is. This made me a bit nervous, so I did some searching on here to find some info.
I read a couple posts about the air and fuel screws, and got to wondering what the settings should be for my sled and when they talk aboout 2 turns out, I am only assuming that would mean 2 turns out from all the way in. Would adjusting either of these richen it up enough to take care of this potential problem I noticed? I guess my other option would be to jet up a size. I currently have 410 mains, and I think stock was 420, but 410 is what I had in there when I bought it used. The only other variable that I can think of is that I have been running ethanol fuel, 89 octane, which I am aware it has more Oxygen, but would that be enough to cause it to be running a little lean? Maybe I am over thinking this and just nervous, but I am leaving this coming Wednesday for a trip up north and want to make sure everything is on the up and up before I get there and have problems. Any help would be greatly appreciated and Thank You in advance. Rich

:sos:
 
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#2 ·
first off, i would check with the dealer, on the stock specs of ur sled, as far as jetting is concerned...

second, the needle on the side of the carb, controls air/fuel, at idle to about 1/2 throttle... you could turn it out a touch, but prob not nessasary...

as I am not sure what carbs are on this, i will give you the procedure, i use, on older round slide carbs....yours might be flat slides... but should be the same either way..

Since it does sound like ur allready leaning out, i would first, move the "C" clips on the needles, down a notch... ie... move the clip towards the pointy end....

then, you take the machine out, find a nice long flat streatch of land,and after the machine is warmed up..pin er in a straight line.....when you hit ur crusein speed, or top speed, hit the kill switch, THEN release the throttle, and coast to a stop....

Then, pull ur plugs, and have a look at em... should be tan, or slight dark... if not, ur still lean, and either have to move the clip again, or rejet with a one size bigger main jet, and try again...

this procedure, ussually works for me, and I prefer to keep my plugs a lil black and wet, as temps here can got from - 5 today, down to -25 tomorrow, and it can be a pain, to redo the jetting all of the time...

Make sure, ur carbs are clean, clean, clean... first.. as a dirty carb, will throw this all way out to lunch....
also altitude, will play a major difference too... the higher you go, the thinner the air, and you end up..... richer...??? ( not sure bout that, memory escapes me, hopefully some one will confirm that part)

Hope this helps...:)
 
#3 ·
Thanks for the info, I will give it a shot and see what I can find out.

I guess I did leave a couple of things out, they are flatside carbs and the altitude I ride in is around 1400'. Normal temps in my area range from 10 lows to 30 highs, of course we get cold and warm spells that change that just like everyone else, but the are usually short lived (except this January, it seems like spring time).
 
#4 ·
i would think your over evaluating the situation i have a 02 800 with carbs i dropped the mains one size cut the heads removed guts in air box installed reeds and never touched the needle or fuel screaws and have 5k miles on with not any probs but a busted servo cable i hve ran in 25 below weather with it so as for being to lean i think your ok they are rich from the factory get some better fuel not oxygenated and see if there is a change in plug color have fun peace
 
#5 ·
430,s were stock for that sled, but know poeple who ran 400,s. Did the other piston look the same? Piston wash is the fuel (washing) the carbon off of the piston. So if the piston is clean = plenty of fuel washing the carbon away. Heres a pic for you to go by.
 
#6 ·
The best I could tell, there was a thin layer of carbon coating the entire piston, but I could not see the intake side of the piston at all. The carbon was not completely black, but was kinda brownish-black. Both pistons have the same spot in the middle of it. The clean spot under the plugs is what is bothering me the most, I guess I would rather run on the rich side than take a chance in burning a piston. I am just looking for the best way to fix this, I really do not have much knowledge when it comes to carb set up and trouble shooting. Rich.
 
#7 ·
Fastkitty, It dont sound like there is a problem. But without looking at the pistons myself I couldnt say 100%. I understand not wanting to break down miles from home or worry the whole trip so go ahead and throw the stock jets back in and forget about it. Wont hurt a thing and the 8 hundy doesnt mind the extra fuel anyway. And when you get back, take another look at the pistons so you can tell the difference the jetting change made. My guess is they will be cleaner yet. Good luck and ride safe. :chug:
 
#10 ·
That spot in the middle of the pistons right under the spark plug is most likely from detonation, not from lean jetting. Detonantion is most commonly caused by poor fuel quality, or not enough octane. Your sled is designed to run on 89 octane, so maybe you have poor fuel or fuel with too much water in it. The first test I would run is to use premium fuel. Syphon out all the old gas, fill with premium and install new park plugs. See if that makes a difference. If it does make a difference then I would look for a different source for regular fuel and see if things stay OK.

The tiny white spots on the elctrodes are likely aluminum from the piston. Once that surface is pitted it can continue to be a hot spot even with no detonation. Any errosion of the piston dome may not be the worst thing, but it is not the best thing.
 
#12 ·
Thanks for the extra input.

94ZR580,
That makes the most sense to me. We have had some unseasonably warm temps for the last month with the lows getting below freezing and highs well above freezing. I see where I could have picked up some water from condensation. My tank is practically empty at this point, so it will not take much to empty it. Please explain to me why it would be good to run a higher octane fuel as compared to Regular 87 octane fuel. I am not doubting you, just so I have the knowledge and understand what that will do for a detonation problem. Rich
 
#13 ·
Originally posted by fastkitty800@Jan 23 2006, 06:54 PM
Thanks for the extra input. 

94ZR580,
That makes the most sense to me.  We have had some unseasonably warm temps for the last month with the lows getting below freezing and highs well above freezing.  I see where I could have picked up some water from condensation.  My tank is practically empty at this point, so it will not take much to empty it.  Please explain to me why it would be good to run a higher octane fuel as compared to Regular 87 octane fuel.  I am not doubting you, just so I have the knowledge and understand what that will do for a detonation problem.  Rich
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I only suggested the the higher octane as a test. One of the causes of detonation is not enough octane, either the result of poor quality, or degraded fuel, or combustion chamber pressures, compression ratio, that requires higher octane to resist pre-ignition. My thought was that if you run premium fuel and the potential signs of detonation stops, then you know that it was a detonation problem. Then I thought you could go back to the regular fuel, from a different source, and see if the problem stays away. The stock engines are designed to run on regular fuel, so generally i would say just use that. You can also use premium fuel to extend your jetting range a bit if you are at the lean end of the range and it is getting colder, but you need to know your limits.
 
#14 ·
Originally posted by fastkitty800@Jan 23 2006, 06:54 PM
Thanks for the extra input. 

94ZR580,
That makes the most sense to me.  We have had some unseasonably warm temps for the last month with the lows getting below freezing and highs well above freezing.  I see where I could have picked up some water from condensation.  My tank is practically empty at this point, so it will not take much to empty it.  Please explain to me why it would be good to run a higher octane fuel as compared to Regular 87 octane fuel.  I am not doubting you, just so I have the knowledge and understand what that will do for a detonation problem.  Rich
<div align="right"><{POST_SNAPBACK}>
[/quote]

I only suggested the the higher octane as a test. One of the causes of detonation is not enough octane, either the result of poor quality, or degraded fuel, or combustion chamber pressures, compression ratio, that requires higher octane to resist pre-ignition. My thought was that if you run premium fuel and the potential signs of detonation stop, then you know that it was a detonation problem. Then I thought you could go back to the regular fuel, from a different source, and see if the problem stays away. The stock engines are designed to run on regular fuel, so generally i would say just use that. You can also use premium fuel to extend your jetting range a bit if you are at the lean end of the range and it is getting colder, but you need to know your limits.
 
#15 ·
I finally got it to the local dealer, 40 miles away. He took a look at it and confirmed what you said about detonation. He said either run 87 octane or 91 octane, but do not run ethanol unless you jet up one size. He said I caught it very early and it would not hurt anything, just make sure not to run ethanol with my current set up.

So THANK YOU for pointing me in the right direction on this, it really set my mind at ease going into our trip this week/weekend.

:beer_cheers: Rich
 
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