Accelerator pump theory

[stockhatch]

So I upped my main jet another size, and also upped the pilot on the Warrior. It runs alot better, and the pop on decel is gone now. Still, though, the off idle hesitation/pop is there when you snap it. I know the squirter pumps on these things suck, but mine is functioning normally and not sticking. What I did note, was that the squirter cam barely pushes on the pump plunger.

There is about 3/16 of an inch clearance between the pump cam and the plunger when no throttle is applied, so when you snap the throttle open, the butterfly/slide shaft has to rotate several degrees before the pump cam even touches the plunger. Then, it only moves a tiny bit, and while you do get a small stream of fuel into the throat, it really seems like it needs to happen earlier, and squirt longer.

The cam does not appear to be adjustable as far as when it makes contact in relation to throttle movement, but I think I can modify the tab on the cam so that it actuates earlier and pumps a larger shot. Has anyone tried this? Any positive results?

I'll post pics when I do this along with results.

 

[DeadLastRacing]

easest thing to do is, take the stock accel pump spring out and throw it in the trash, take apart a retractable pen and use the spring out of that. Its a whole hell of a lot stronger and a lil bit longer. Which will move the pump pole up more towards the tab.

 

[yamarider]

I don't remember having that big of a gap between the plunger and throttle wheel when I had my stock carb on the warrior. My guess would be that the spring isn't fully returning the plunger to the highest postion. If that doesn't work, bending the tab on the throttle wheel would probably do the trick, just don't break it because you'll probably have to rig up the repair, that part isn't available as a seperate replacement.

 

[stockhatch]

Hmmmm. I thought for sure the plunger was returning fully. I even grabbed it and pulled up on it with some needle nose to verify it wasnt a weak spring. I also stretched the spring last time I had the bowl off as a precaution, though I have never seen the plunger bind...I'll double check it this weekend and snap a couple pics. Can anyone verify the proper gap between the pump and plunger, or possibly the plunger height from the housing base?

Thanks

 

[stockhatch]

easest thing to do is, take the stock accel pump spring out and throw it in the trash, take apart a retractable pen and use the spring out of that. Its a whole hell of a lot stronger and a lil bit longer. Which will move the pump pole up more towards the tab.

I'll try that too.

 

[stockhatch]

Well that didnt work too well. I ended up bending the actuator to position the cam just about against the plunger. Maybe .010 clearance between them. Well, it seemed to help, but the problem is definitely still there. If you jab the throttle, it still pops and tries to die. You can roll into it faster, but anything considered stabbing it is a no go. I dont remember it acting like this before I piped it and put the K&N on it. Is it just that the stock accel pump cant physically supply enough fuel for a modded bike?

 

[stockhatch]

I guess I will go ahead and ask, does the Edelbrock carb improve over the stocker enough to justify the cost? If I knew it would solve all my problems I would go ahead and get one, but I dont want to spend $400 to find it is only a marginal improvement.

 

[91warrior]

i just got one a couple of months ago. i was having problems after my rebuild with the stocker that it would cut and miss and carried on and i tried changing and messing around with every jet but couldnt get it to clear up. so i bought and edelbrock and before even jetting it it could ride it normally for once. but i still had that hiccup with a quick jab of the throttle.

now im at college so i only get to mess with it every now and then. at first i adjusted the needle and still had the hiccup. last time i adjusted it, i adjusted the accelerator pump and that really helped, almost cleared it up. however, it still has a very slite hiccup if i twist my throttle the fasted i can, but if i just "roll" into the throttle fast instead of just instant WOT, it seems like it pulls a lot harder. but im sure i just need to get it dialed completely in. but i have no regrets getting it, just need to spend more time with it.

 

[stockhatch]

Thanks for the feedback. So with the Edelbrock, can you get different pump cams and different cc squirter?

 

[DeadLastRacing]

I got myself a edle as well.......still moddin the engine so i cant say just yet how big of i difference it will make but from what I read its a great upgrade and especially for a moded engine.

 

[yamarider]

The stock carb will always have a hesitation if you jab the throttle hard, no way to get rid of it, it's just too weak of a fuel stream. Messing around with the fuel screw can help optimize the throttle response though. Compare the weak little dribble the stocker puts out vs the super-soaker like blast a tuned flat slide has, and the lack of sufficient fuel is very evident. The stock carb doesn't have enough to eliminate the hesitation on a stock engine, much less a modified one.

I had an Edelbrock, and when you have one tuned in just right the throttle response is instant. Not quite as good as fuel injection, but way better than the stocker. The accel pump is adjustable by a screw, no different size nozzles or cams required. Just turn the screw. That was my favorite part about the edelbrock, it was much quicker to tune than a conventional carb. Tuning the idle through midrange fuel mix took a matter of 15 seconds or less, and swapping out the needle to change the top end is still quicker than changing out a jet on a standard carb.

What I really didn't like about the Edelbrock though, is that it doesn't have a choke. No big deal if you're a warm weather rider only, but I like to play in the snow and ice too so I got extremely annoyed by it, it's probably one of the reasons I got tired of the warrior and bought my fuel injected rappy. I'd have to richen the edelbrock and play hell to get it started at all, then once it warmed up i'd have to shut it down and lean it back out a few clicks for it to run right. I feel they are a bit overpriced too, I've spent the same on a 4 barrel edelbrock for my car which is a much more complex design with infinitely more moving parts. It just doesn't make sense to me, other than the cost will be a little higher since they production numbers are lower.

If I were to do my warrior over again, there are a lot of things I would do differently. One of those things is using a Mikuni flat slide carb over the Edelbrock. Probably a little more work in the initial tuning, but you have more control over the fuel to get it just right, and it even has a friggin choke... I will probably never understand why Edelbrock skipped this on a carb for an atv. Do they think we just stay inside and sip coffee all day when it's cold?

 

[91warrior]

yep agree with you there yamarider, it does suck not having a choke. takes longer to get running but the tuning on that carb is very simple, i just dont have much experience with tuning yet.

 

[stockhatch]

Great info guys. Thanks alot. I am also looking into a Raptor 350 carb, or the Z400 conversion. I think these can be had much cheaper than the Eddy and do the same thing it can. Is that a fair assumption? How is the throttle response on the Z400 Raptor carbs? Tuneable? Sufficient?

I know there are threads on this, but I have scoured the forums searching 2000 days back, and read everything I found. Some of it is old, and some is inconclusive or vague. From what I found, the Raptor 350 and Z400 carbs are the same? They both need a boot stretch on one side and the Raptor boot on the other, and require three jets including the pilot? I'll keep reading, and may pick up one carb or the other to play with. Between the two, is there a better bolt on? Raptor 350 vs Z400?

Thanks again to all you guys who have been there and done that. The old Warriors are kinda becoming the forgotten stepchildren, but they're affordable, and overall I really like mine. I just want to make it more responsive off idle so wheelies are easier

 

[yamarider]

If i'm not mistaken, I thought the stock z400 and rap 350 carbs were CV carbs, which i'm not a huge fan of. Throttle response is slow and they tend to be unreliable and more difficult to tune in. I'd try to find a decent used flat slide carb instead.

 

[DeadLastRacing]

just missed out on a 37mm , round slide mikuni for $46+ $15s/h

 

[stockhatch]

If i'm not mistaken, I thought the stock z400 and rap 350 carbs were CV carbs, which i'm not a huge fan of. Throttle response is slow and they tend to be unreliable and more difficult to tune in. I'd try to find a decent used flat slide carb instead.

Are there any particular models I should look out for?

Thanks

 

[yamarider]

I don't know any models specifically, just a mikuni around 36-38mm with a flat slide and accel pump. Make sure you know the inlet and outlet sizes before you buy, you'll need a way to connect it to the intake manifold and airbox, and the stock intake manifold definitely won't work. Where you get one will depend on the size of the carb.

If the carb is too long it might take more customization than you want to get into, the stock carb is pretty small so a larger one could require all kinds of stuff. It's kinda hard to say until you have the parts in hand and start seeing how it all lines up.

If you want to play it safe, get something that has been tested on a warrior before so you know what you're getting into and can at least get some baseline jetting.

 

[stockhatch]

At this point Im seriously considering the Edelbrock. It should come in kit form and just bolt in right? i have found it for $350 shipped, and if it is awesome with the exception of being chokeless, I may just go for it. Its warm around here pretty much year round anyway.

 

[91warrior]

yea the edelbrock is a bolt on kit, just the fuel line is a little big where it connects to the gas tank, i had to use a hose clamp for it to stay on. took me about an hour because i was having a hard time figuring out the cables for the twist throttle.