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Discussion Starter · #1 ·
Just picked up a 1995 Zr 700. Previous owner said that his son ran it out of gas and then upon refilling it it started to backfire. I'm not sure if all the time or at certain RPM. Any ideas? They switched out carbs and coils' with a running sled to check. So it's probably electrical? CDI possibly?

Thanks for any leads!
 

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Check to make sure the gas isn't bad/rust in the tank....ect.
 

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check the switches on the carbs that control the moniter system for the throttle. you could have a bad reed also. I had a 94 that would backfire so I just bypassed the carb switches and it stopped.
 

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Discussion Starter · #4 ·
Thanks - I'm more into the vintage stuff so learning as I go. Never worked on Reeds - I hear they need cleaning? Carbs I'm getting good at. The rest of the sled is pretty good - not mint by any means but not bad. I paid $400 - has 2800 supposedly on the chassis. Seems a little more like 5k but who knows. I had a gut feeling it would be something like TPS or fuel related - so took a chance. figure could part if needbe!
 

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the red on that machince are actually mounted to the bottom of the cylinder so they are hard to get to. you can take off the carbs and stick your finger down in the port( port is just behind the flange where the carb mounts). You could also have picked up some junk from the bottom of the tank like stated above or some how you have a bad seal. Its alway fun (sarcasam) tryin to find a problem when there is no apperent reason. Good luck!
 

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Discussion Starter · #6 ·
So how does one go about cleaning a reed thats buried in a hole lol. And what the heck to they do?


I'm thinking it's gotta be fuel related since it happened immediately after running completely out of gas!
 

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Unfortunatly the only way to get to the reeds on the old zr is to remove the cyl. The reeds are kinda like a one way intake valve, as the piston goes up it pulls fuel and air in throught the carb and down through the reeds into the crankcase then as the piston comes back down it creats postive pressure in the crank case wich closws the reeds and forces the air fuel mix up through the transfer ports. You dont really clean the reeds just replace them. Just feel down in the port and you will know if one is broken. Might just have water in the carb also.
 

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That a bummer. Its not a bad purchase but you may not have gotten all the details.
 

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I would just forget anything the guy told you after hearing the running out of gas and then started backfiring bs. Here's generally the way i would go at it.
1 do a compression check. if ok
2 make sure carbs are clean, jets clear, float height set, and gas is fresh. if ok
3 fresh spark plugs and check for good spark. if spark not good meter the stator with ohm meter. if ok.
4 check if plugs are wet (excessive flooding) clean choke plungers and adj to seat properly.

if still not good, I would bypass all chassis electral wireing at stator to elimonate any shorting wires or switches.

If still not fixed. Get case of beer guzzle quickly. Read Manual. Good luck.
 

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Discussion Starter · #11 ·
Awesome reply lol

I do have about 8 other project (vintage) sleds in dad's pole barn - half a mind to just dump it for what I have in it. BUT part of me wants to see if it'll run without much work.


He did respond that it backfires ALL the time - Both plugs were very dark. Also evidence of that at the exhaust manifold fittings - fresh black unburned yumminess there.

Compression was 130 on PTO, and about 118 on MAG. Mag i might've pulled a little less intense. Cold - 3 pulls with WOT. I know supposed to be within 10%?? Thats pretty close I figured.....
 

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IMO that is quite a big difference in compression it shouldn't be any more than five pounds within each other it shouldn't be lower 125psi i think you should try again and see what you get if the readings don't change i would probably pull the cylinders off and re ring it and wile the jugs are off it'll give enough room to check the reeds !
 
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