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Discussion Starter #1
Hey all....new to the forum, hoping to get a little bit of expertise on some trouble I'm having with one of my Warriors, before I really start tearing into it. I just got it - currently it's very difficult to get started without choke and once you get into higher RPMs it likes to backfire out of the exhaust and carb. Once it's up and running you can beat it into submission and tear it up but definitely doesn't sound good Let me start with a few details on the bike:

  • Whole top end was rebuilt by Yamaha and bored out in the process. The paperwork I have on this says standard is 82.95mm, the shop bored it to 83.45mm. I don't know much about detailed engine work like this.
  • Carb looks to be made by "Zoom Zoom"...never heard of this and don't know if it's some junk carb I should be concerned about
  • Pilot jet is 42.5, I think the main jet was a 145 when it was backfiring....the PO put a 155 main in it but hasn't been tested at full throttle
  • HMF slip on
  • Bike had some strange K&N style mini air filter that clamped directly onto the carb, eliminating the airbox. Not sure what the deal is with that. PO hooked up the airbox which has a full size K&N and airbox lid
  1. I know jetting is a process to figure out, done it many times. What kind of baseline jets do you think I should start with, given the mods to the bike? Just as well - what should I set the A/F screw to?
  2. Do I need a different spark plug with the bore job?
  3. Anything wrong with the air filter setup? Should I stick with that "mini filter" and ditch the airbox, keep the airbox and K&N, or keep the airbox and swap the K&N for foam?

Like I said, I don't know much about detailed engine work so I don't want to be wasting time when it could be something obvious related to that. I'm thinking it's running very lean and am leaning towards a 45 pilot, 155 maybe 160 main and A/F 2 1/4 turns out with the airbox and K&N.
 

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Discussion Starter #2
Oh...and one more thing regarding jetting. Would you recommend any changes in the needle position? I've never adjusted on my other Warrior so I'm not even sure if you can adjust them on these bikes.
 

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zoom zoom is Chinese carb sometimes they are ok sometimes crap. jetting sounds lean but 160 is getting pretty up there unless you live at sea level. the needle fine tunes the main. lowering the clip/raising the needle will make it richer and bring the fuel in a little sooner and vise versa. what does your plug look like. my guess is if you are lean with the 155 its not jetting. most likely culprit is the intake boot. they can look fine on the machine but when you take it off you can find hidden cracks or bad orings. i could be that zoom zoom i have seen them with the castings so bad the ports are blocked but i had one on a 96 that ran like beast. go back to the air box and big filter. leave the lid off and run a pre filter on the big k&n. if the intake is good you might go up one on the pilot. if you are not on a tight budget i really like the jd jet kits it offers a couple different needls depending on altitude and mods and give you several jetting options and a great guide to match your mods. there needles have a better fuel curve imo. also check the valve lash
 

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I figured as much regarding the carb. Makes me wonder whether it's worth it to buy a beat up Mikuni for $50 and rebuild the thing. The plug is very black right now, but I would disregard because it's been in there (uncleaned) after several jet changes...not to mention the PO flooded the hell out of it cranking it over so many time trying to get it to start. Definitely will at the very least give it a good cleaning - may just throw in a new one to be safe.

Thanks for the tips on the intake boot & valve lash. I have not checked the boot yet but very well could be causing problems. I'll check out JD jets...never heard of them, usually use dynojet or jets-r-us.

I think ultimately I'll get it to a good jetting baseline with the K&N (which already has a prefilter, forgot to mention) and see how she does.
 

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Discussion Starter #5
Alright....update on the situation. Gave the carb a thorough cleaning, adjustments and it's got a 42.5 pilot/155 main, A/F screw 2.25 turns out and stock clip on 3rd rung. There were a few parts missing and just about everything was adjusted wrong. I threw in a used, but clean spark plug (didn't have any new ones on hand). Hooked up stock airbox setup with large k&n and prefilter, with the lid on. Also cleaned out the gas tank.

The thing fired right up, ran great. Rode it around my yard in forward and reverse, no issues at all with how it ran....of course I wasn't able to get into the higher RPMs. Only thing I noticed was the carb bowl was weeping gas very slightly where it mates to the carb...I stupidly re-used the old gasket since it seemed OK. Figured I was all set though, it ran! Well....decided to throw a new clutch perch on there, as well as a new carb gasket...and now it runs like shit. It'll idle just fine but if you give it any gas, it starts cutting out...almost as if it's the rev limiter kicking in. Doesn't matter where at in the throttle range, it just "sputters".

SO I would love to hear what you think may be the source of my problems. I did NOT check the intake boot or valve lash yet...I was going to but it ran fine after my initial rebuild, like I said. Not sure if those 2 items could be the source of my trouble - if you think so let me know and I'll check them. My thoughts:

  • When I changed the clutch perch, the parking brake had already been eliminated by the PO (block off plate and all). I just unplugged the bullet connectors for the clutch under the dash and plugged them into each other to complete the circuit. If I remember right clutch wire issues will cause a no-start (?) but parking brake wire issues will cause "rev limiting" conditions.
    • When I eliminated the parking brake on my other warrior, it had a white plug connector under the dash. I just unplugged it and filled it with di-electric grease. I cannot find that plug on the problem warrior? Do you think the parking brake wires could have been shorted out or something? How can I trace where these went if so?
  • When I changed the bowl gasket, I did it with the carb on the bike (I usually remove the whole carb but was being lazy). Is it possible something got jammed up in the process of sliding the bowl back on - ie. the little plastic washer that goes around the main jet, the accelerator pump etc. Not sure if any of these would cause this condition...figured it's worth mentioning.
  • Possibly the spark plug went bad?
 

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Ok, I’ll give those a looking over. Do you have any idea where the parking brake wires lead to ultimately? If I can’t find the plug I would like to trace them...just to be sure they aren’t shorting for some reason.
 

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Ok, checked the intake boot last night and it seems to be solid. Checked valve lash and adjusted both, and checked timing while I was in there. It seemed to be in time already, but not perfectly lined up with the notch on the head (though I might be crazy so I'm attaching a picture). With the chain on and tension on it I had some slight free play where I could line the gear up perfectly by hand, but the tension on the chain would pull it back to where it naturally sits. If I jumped it a tooth over, it goes too far the other way. Does this look acceptable to you?

6368
 

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it is never dead nuts on could be a worn timing chain. how much play does it have. could be a partially sheared flywheel key as well.
 
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