Mikuni "pulse" fuel pump on gravity fed tank? Yt175

[Hasteranger]

I have an 83 yt175 with a mikuni pulse pump plumbed between the tank and carb (stock setup). From what I read, the 81 and 82 models did not feature the pump and stuck with gravity feed. When I was trying to get mine to start, I bypassed the pulse pump and went straight gravity feed. Guess what? Works fine.

So now I'm debating whether to eliminate the pulse pump with its extra lines, clamps, and fittings, or to keep it, assuming the engine still runs when I hook it back up.

What's the advantage to using this pump? What was "wrong" with the earlier years that they corrected with the pump?

[shortline10]

If theirs ever an issue with the float valve sticking it stops the fuel from entering the carburetor while not running and hydraulic locking up . I get a lot of bikes threw my shop with this issue .... cylinder full of gas and even the bottom end full
Yamaha loves to build their motors with the carb leaning toward the motor so if and when the carb fails gas goes straight into the motor .....

I have an 83 yt175 with a mikuni pulse pump plumbed between the tank and carb (stock setup). From what I read, the 81 and 82 models did not feature the pump and stuck with gravity feed. When I was trying to get mine to start, I bypassed the pulse pump and went straight gravity feed. Guess what? Works fine.

So now I'm debating whether to eliminate the pulse pump with its extra lines, clamps, and fittings, or to keep it, assuming the engine still runs when I hook it back up.

What's the advantage to using this pump? What was "wrong" with the earlier years that they corrected with the pump?

[Hasteranger]

But are the pumps themselves reliable? Seems like a bit of a trade off with the extra vacuum line and all that. From reading online, the pulse pumps were used in applications that either didn't gravity feed, or didn't gravity feed well. Seems like an over the top solution to a float sticking. Especially when turning the petcock off when you're done riding is a free solution to that problem.

[shortline10]

With todays fuels the rubbers go bad quickly and honestly how many people turn their petcock off after riding ?
If your like me I always turn them off so a gravity feed petcock is fine just not for the general public .

But are the pumps themselves reliable? Seems like a bit of a trade off with the extra vacuum line and all that. From reading online, the pulse pumps were used in applications that either didn't gravity feed, or didn't gravity feed well. Seems like an over the top solution to a float sticking. Especially when turning the petcock off when you're done riding is a free solution to that problem.

[Hasteranger]

Well I guess let me put it to you this way:
If you had an 82 with gravity feed, and it ran fine, you wouldn't add a pulse pump to it, would you?
I have an 83 that is running ok now with it bypassed (for trouble shooting) and I can't think of a good reason to hook it back up, on that logic. Honestly had never seen or heard of one of these things until I took the tank cover off.

[YTZ drew]

You may want to consult the parts fiche for the float needle & seat in the carburetor. If 81-82 didn't use a pump, they are probably different than the 83. Gravity feed carbs usually have a larger needle and seat than ones meant to be hooked up to a fuel pump. If you just delete the pump, it may be fine at idle and low speeds but starve for fuel on the top end if you have the smaller needle and seat.

[Hasteranger]

Do you know where I could find that? I did a Google search and turned up with dimp.

[shortline10]

http://www.partzilla.com/parts/searc...ANK/parts.html

[Hasteranger]

Ok cool. They are the same. Both unavailable, too.

[350for350]

Haste, for what it's worth, I'm in the habit of turning off the petcock after every ride. Not that it matters to anyone else. I also have friends that do the same thing.

[Hasteranger]

Yeah I always do on everything I own. Ever since the ethanol gas I make sure I do. It's not gentle on these small engines. I'm lucky to live near a liberty that still sells ethanol free gas now, but still.

[YTZ drew]

Ok cool. They are the same. Both unavailable, too.

In that case, try running without the pump. You may have no problems at all. My guess is that Yamaha put the pump on there to address some fuel starvation issue they were experiencing on the older models. Your riding style alone may be the difference between needing the pump or being fine without it.

[El Camexican]

Is it the one on the far left of this link?
http://www.sudco.com/fuelpumps.html
I'm guessing it is. Mikuni only makes a few different pumps.

My 1979 & 1980 YZ80's had this pump as did many sleds. The one vehicle that did not us this small pump was the Tri-Z. I don't know why Yamaha decided the larger pump was needed, but they did. I'd run the pump if it came on the bike, but if you do remove it make sure the vacuum line is well sealed.

[Hasteranger]

Yeah you can see it on the left here. http://s57.photobucket.com/user/andr...5qc4u.jpg.html

When I get somewhere where I can run the bike pretty decent I may try it with and without. I have a guess, and that's that the fuel tank is only a few inches higher than the carb, so if you went down a long steep hill or dune maybe it could stall out?

[El Camexican]

Stalling out is the least of your worries. Running out of fuel on a 3 mile top end run is what you want to avoid.