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Discussion Starter · #1 · (Edited)
Issue goes like this, last week it was deep cold here, 6, didn't want to fire off.... (note) I've never touched the primer till now and after i did, (stock 99 fourtrax 300 4wd) she finally fires so i went on my way, i noticed a new issue, after i let up on the throttle she drops in rpm for a few seconds, then returns to normal rpm ( 1400 ) + or - 100, she acts like there's a moment of rich gas dumped into the chamber, my question is, can the primer cause this issue, i wanted to run this by you fellows before i purchase a new oem and has plenty of low and high rpm performance no other issues besides the above, shop manual is no help,

GENUINE-HONDA-CARBURETOR-PRIMER-PUMP-KIT-16048-HN7-003

Checked out good:
1 plenty of clean fuel
2 spark plug is firing as it should
3 fuel filter/screen spotless
4 air filter clean and foamed
5 petcock on, lol
6 gas is getting to the carb perfectly
7 vent in gas cap working fine
 

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I wouldn't think that would be primer related, unless it stuck or is leaking.

Sounds more like a temperature related issue. Here I had a frozen vent on one bike and another that is a little lean so it struggled in the cold, but ran fine until it got into single digits.
 

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I’m with Jeep in this one.. it’s been freakishly cold, I’ll bet moisture set is and froze up


Sent from my iPhone using Tapatalk
 

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Discussion Starter · #4 ·
Thanks guys! Could be moisture, but ...... I have always kept the tank topped off all the way up to the neck vent hole, right under the gas cap, and i never use reserve, it was warm today, still does the same thing, cold or hot, my bad for not adding that fact, no leeks at the primer, could the cause be some trash that was some how or another broke loose when i primed her ? I'm still blank on this issue, ..... Cause she's always ran like a sewing machine, I'll check the plug TM for carbon build up, and check the exhaust for black fluffy carbon, she seems just on the verge of cutting out , only thing i can think of at the moment is taking off the air filter and covering the intake with my hand and turning the engine over to dislodge what ever is causing this, i can't think of anything else i should check, I'll update soon, thanks again guys, very helpful !
 

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I can't see the primer having an effect on the way it runs , unless there is trash in the carb and you swooshed it around by priming ------------ I know I would not pay $50 for a OEM primer pump from Partzilla , the ones off e-bay for $10 have worked fine for me for a long time , Chinese parts are usually junk but this is one I do , the local dealer of ATV/UTV's Friendly Power Sports in Slidell told me $90 for one primer for my 300 , I didn't get it , they are so much higher than any of the other dealers in the area , double on a lot of things I price from them as compared to Picayune or Covington
 

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Discussion Starter · #6 ·
Yeah fish flushed around trash is what I'm thinking, so i went back out and drained the carb, the gas looks perfectly clean, NO sign of trash, filled it back up primed it again, primer did build a bit of back pressure and sprang bck out like normal, no leeks, so i drained it again, same , perfectly clean gas ......... I collected a sample and I'll let the fine trash (if any) settle for a while and see.....
 

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Discussion Starter · #8 ·
Thanks fish, and this morning the light revealed trash in the sample......s I'll be pulling the primer pump for inspection.....
 

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Discussion Starter · #9 ·
I wouldn't think that would be primer related, unless it stuck or is leaking.

Sounds more like a temperature related issue. Here I had a frozen vent on one bike and another that is a little lean so it struggled in the cold, but ran fine until it got into single digits.
Okay ....... She ran fine today , no drop in rpm, question........ If the vent line is pluged..... When i drain the carb bowl, will a pluged vent be a tell tell sign ? Or will it drain never the less ( slowly ) cause mine drained faster the further out i un screwed the bowl drain screw
 

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primer bulb

i capped off my primer bulb on the 2000es. i didnt cap off the feed. if sediment can get there any where, it will. i forget the rule, but, if it can happen, it will happen. maybe not for you, but for someone. i didnt know primer button was so cheap when i capped mine. for that price, i will replace what i got. seemed like it was over $50., back then.:big-grin //Ed
 

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Okay ....... She ran fine today , no drop in rpm, question........ If the vent line is pluged..... When i drain the carb bowl, will a pluged vent be a tell tell sign ? Or will it drain never the less ( slowly ) cause mine drained faster the further out i un screwed the bowl drain screw
A plugged (or iced up) vent probably wasn't an issue here, since the motor ran fine under load. I'd guess that it was just colder air than the carb was adjusted for (as air temps drop air density increases). A slight turn (out) of the pilot screw might have verified this.

I go through this same idle mixture issue all the time on my snowmobiles, since I'm jetted pretty close to optimum for 10 degrees (F) air temp. When temps drop below zero I gotta open the hood and add 1/8 turn out on each carb or I lose some throttle response and the idle becomes weak. Then as air temps warm up I have to screw them all back in... routine stuff.

I sometimes see a lot of heavy icing forming inside the carbs (around the throttle slides) on my sleds when the motors are first started cold too, so it is possible that you got a thin sliver of newly formed ice stuck in the air bleed passage that cold morning. I've had that happen to me before.

As far as being able to detect a clogged vent by watching how fast the fuel in the float bowl drains...? I doubt you'd notice any difference in fuel drain speed or volume because the motor is not running while you have the drain screw open. So air at atmospheric pressure is able to enter the bowl through the top of the Needle Jet (emulsifier tube) and through the large air bleed passage (in the carb bore at the base of the venturi) bypassing any clogged vents you might have. A running motor won't see atmospheric pressure anywhere inside the carb except through a bowl vent (and through the air bleed passage), so thats when you might notice fuel won't exit the float bowl.
 

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Discussion Starter · #12 ·
Something else is happening..... Engine denotation (knock) JUST. (Never did this before) On start up, my new question is, if it just happens on startup, should this be a concern ? IE ( engine damage ? ) And what could be the cause of this new issue, added it only happens when the engine is warm...... Could this be a the NGK iridium spark plug i swopped to ? I run only 87 octane gas, treated with red stabil .
 

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If it spark knocks on startup (assuming this is not a mechanical problem) its generally a temporary problem due to an aged fuel/lost octane issue. If it is an ethanol-laced fuel it might have been rotten straight from the pump.

Other causes for pinging are excessive carbon buildup in the chamber and/or excessive motor oil getting into the chamber. Think worn & leaky valve seals, worn out piston/rings, broken ring, etc. Motor oil in the chamber used to be the number one cause... but nowadays its generally a rotten fuel issue involving the ethanol scam.

EDIT:
Forgot to mention... Stabil treatment is only effective if using non-ethanol fuel. Minimum octane rating of fuel should be 89 (and fresh) before adding any treatment additives. Treating ethanol laced fuels are like putting lipstick on a pig. Ya can't turn garbage into gold... Let us know if fresh fuel fixes it...?

Check around the intake for a cracking or leaking carb boot too.
 

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real fuel v/s ethanol fuel

retro; if you are in a place where you can get 87% non ethanol fuel, would you have to add octane to it? also, i thought some of those fuel stabilizers were created for ethanol fuel. perhaps i need an ED-ucation. //Ed
 

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Its cheaper (and more effective, since many/most octane boosters are a misunderstood scam) to buy a mid grade or higher fuel in the first place.

There is a Stabil product that is formulated for ethanol laced gas (its not very effective) and one that is intended for non-ethanol gas. I use the original red label stuff sometimes myself. My point about using a stabilizer for 89 octane minimum fuel is that with 87 grade there is nothing there to preserve (poorest, cheapest grade available, with winter grade gas being the worst possible fuel) in the first place, so its a waste of your additive. If you buy low grade fuel it should be consumed immediately with fingers crossed.

And if you buy ethanol laced fuel of any grade there ain't no fixing it no matter what... or any hope for effective short term storage of it... Ethanol contains significant percentages of water and other organic impurities along with oxygen, so it is bio-degrading rapidly from the moment it is created and will continue to rapidly rot until all oxygen-driven chemical reactions cease.

I'd simply change the fuel in the tank to a premium (non-ethanol) grade during the winter months if you are having problems. Winter grade fuels are not your friend...
 

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I had some trouble getting non-ethanol fuel last Friday , with all the ice on the roads during the week the deliveries were backed up and the station I usually go to was out , I had to drive 10 miles out of my way to another station that had it , but it was worth it , I usually buy 20 gallons at a time , add Red Stabil to the storage cans and a shot of Sea Foam to every tank fill

ironic this thread is about fuel primers , Sunday I rode my wife's bike when mine had a problem , I jumped on it and didn't check the fuel , so after about an hour I ran out and had to switch to reserve , I tried to press the primer valve and it is stuck solid , I was just going to change the primer , but think I should pull the carb off and see whats going on inside , have never had that happen before
 

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Discussion Starter · #17 ·
Thanks for the info guys, IF...... I have time I'll be testing between spark plugs and I'll be pulling off the primer, can the knock (ping) on startup cause any engine damage ? Or..... Is this the nature of honda engines ? Fish...... Same aggravation here ...... I should have never touched that dang primer, little Johnny had always said as they age they can cause issues. EI leeking , sticking, and (yes) as fish stated swooshing up trash, i don't think this is an oil issue, cause I've never had to add any at all, again it might be my misstake adding a bit because now she's a tad over the upper mark, so I'll be pulling some back out , that part I'm happy about i didn't account for the high tire pressure in the front over 10psi and only 2 psi in the back .
 

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...can the knock (ping) on startup cause any engine damage ? Or..... Is this the nature of honda engines ?
Yes, it certainly can (and will) damage the motor. No, its not the nature of a Honda motor. Since this might be a winter grade fuel problem, you'll probably need to buy a premium grade of fuel to solve this problem... at least until the refineries switch back to supplying summer grade fuel again. I'm interested in what you discover...
 

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Discussion Starter · #19 ·
Thanks! Retro, i sure will post my findings, hope it warms up some so i can get this issue adjusted.
 
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Discussion Starter · #20 ·
@SamUK turns out i didnt have a pic so......here's a pic of the NGK 8eix-9 the 7ea-9 plug is the same exact colour.
 

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