Fuel Pump Question 99 M750

[cauliflower ears]

Ive done a lot of searching on the forums and I can't quite find the answer I am looking for.

I have a 99 M750 that I got recently from a buddy and I have resolved all the issues but this one. The bike wont start but I can get it to fire up with the help of starting fluid in the carb. It starts right up then dies once it's burned everything off. I can assume (I know I should not do that) that the bike is starving for fuel and that's why it wont stay running or start on it's own. I have replaced the fuel lines, fuel filter and new battery. Up next was to look at the fuel pump.....

I removed a line from the fuel pump to the carb to see if fuel was actually being sent to the carb. How much pressure should the fuel pump have when sending fuel to the carb? Should it be like a firehose or a bubbling brook just trickling out? I have to say that mine just bubbles out and I think that it is the issue. Replacing the pump is not an issue (Hoping it's cheaper than my 998 and 999) but I was hoping to just clean it out. I found a thread about soaking it in pinesol?? Is there a better solution or should I just suck it up and buy a new one?

Thanks!

for your replies

[Speeddog]

You could try bypassing the vacuum operated 'petcock' valve (if it's still on there).

For the OEM pump, you can get a rebuild kit from Sudco.

Or you can buy a slightly different pump as a replacement from California Cycleworks.

[cauliflower ears]

Thanks for the reply Speeddog!

It does have the petcock (I believe that is mounted just above the shock??). I'll see if I can bypass it and if it resolves the issue. I just want exhaust all possible solutions before I buy a new pump...to only figure out it was not the pump but something totally simple.

[Speeddog]

If you do bypass the vacuum petcock and find that solved the issue, best to install an in-line manual petcock.

Otherwise if you stick a float valve and the bike sits, it'll happily dump a good bit of gas into the crankcase.
Not a good situation at all.

[ducpainter]

If you do bypass the vacuum petcock and find that solved the issue, best to install an in-line manual petcock.

Otherwise if you stick a float valve and the bike sits, it'll happily dump a good bit of gas into the crankcase.
Not a good situation at all.

I'd recommend dumping the vacuum petcock and replacing with a manual either way.

It can also dump fuel into the manifold via the vacuum line with the same result.

[koko64]

My money's on the vacuum petcock .
Putting a kit through the pump or cleaning it is a good idea if the bike has sat for a long time.

[memper]

My money's on the vacuum petcock .
Putting a kit through the pump or cleaning it is a good idea if the bike has sat for a long time.

I second that. I have a 99 750 and mine crapped out. Plenty of cheap manual petcocks out there. Just don't look too pretty. But then again, neither does having a bike that won't start.

If you in fact do need a pump, I have one lying around.

[cauliflower ears]

Thanks everyone for the info, it's been a wealth of knowledge on this issue so far.

I did forget to mention that the bike sat for almost 6 months.

Just to make sure I am looking at the correct part, I would connect the two hoses together to do a bypass test? The two hoses are at the 9 and 3 o'clock position? What about the hose on the front?



Thanks everyone again for your answers.

[cauliflower ears]

I second that. I have a 99 750 and mine crapped out. Plenty of cheap manual petcocks out there. Just don't look too pretty. But then again, neither does having a bike that won't start.

If you in fact do need a pump, I have one lying around.

If it's the petcock it's gone! I am not showing my bike so I could care less what it looks like vs. how I can still ride it.

[ducpainter]

Thanks everyone for the info, it's been a wealth of knowledge on this issue so far.

I did forget to mention that the bike sat for almost 6 months.

Just to make sure I am looking at the correct part, I would connect the two hoses together to do a bypass test? The two hoses are at the 9 and 3 o'clock position? What about the hose on the front?



Thanks everyone again for your answers.

Connect the two large diameter hoses together.

The smaller diameter hose is the vacuum line that is supposed to open the petcock by manifold vacuum.

If the bike sat for an extended period you might have an ethanol related issue.

[cauliflower ears]

Weird update to this issue.   

The bike wont start but here is all that I have tried: 

- New Fuel Filter
- I bypassed the Petcock (I just plugged the two big hoses together)
- Removed and cleaned the fuel pump (sandy and nasty)
- New plugs
-Tested that the plugs are getting a spark

I am 99% sure the carb is getting fuel. I pulled the line that goes to the carb from the pump and there is fuel coming out. It does not shoot or rush out...it is more a trickle. When I try to start the bike I can actually smell gas coming from the carb (I have the airbox apart). I can start it with starting fluid and it will do a quick idle before I assume it burns off the fluid. If I try to give it gas when its started with starting fluid it instantly dies.

This is just a head scratcher to me, it seems like it should work but it's not    The only thing i have not done is pull the carb off to look at it. I might try that next if I cannot figure anything else out.

Thanks again for all the great replies. 

[ducpainter]

Have you drained the float bowls?

How long did the bike sit?

[ChrisK]

He mentioned earlier it sat for 6 months.

[ducpainter]

He mentioned earlier it sat for 6 months.

Thanks...missed it.

I think he has clogged pilot jets, and or mung in the float bowls.

[cauliflower ears]

Thanks...missed it.

I think he has clogged pilot jets, and or mung in the float bowls.

Awesome I am on it! It could be float bowls.

Thanks again everyone!