DR750 Fuel Vacuum pump

Questions regarding the DR750

DR750 Fuel Vacuum pump

Postby gadgetboy » Mon Dec 18, 2017 3:17 pm

Hello All,

I am new to the forum having recently purchased a 1988 DR750. Its a french import now registered in the UK.

During my recent recommissioning work, I have noticed the fuel pump isnt working. i found an old thread here which mentioned a few alternatives to the £130 OEM replacement pump from Robinsons Foundry. Problem is, none have 100% confirmed that they are running well with the alternative pumps without any issues such as fuel flooding the carbs and exiting from the air box etc.n :crazy:

The options are;
SV650 vacuum pump
Mikuni DF44-211 SINGLE OUTLET ?
Ducati monster pump?

I hoped someone has replaced their std. DR750 pump with something affordable and can vouch for the reliability having used it for some time. If not - perhaps someone knows what the DR75 vacuum pump specification is? if we know what flow rate (L per Hour) is and the PSI, then i can pass this info onto Allens Performance and find a suitable aftermarket Mikuni item to use!

Many thanks in advance,

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Re: DR750 Fuel Vacuum pump

Postby gadgetboy » Mon Dec 18, 2017 3:41 pm

Sorry, i should have mentioned that the fuel pump fitted to my DR750 was not OEM, it is a mikuni one off a Suzuki SV650 one by the looks of it, so the repair kits mentioned on this forum are not the correct shape for my damaged pump..

Thanks!!
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Re: DR750 Fuel Vacuum pump

Postby O.R. » Mon Dec 18, 2017 4:53 pm

The BIG has a mikuni Pentagon fuel pump, vacuum operated with single outlet. Repair kits are available.
The first fuel pumps have a spring which need to be removed for use of the latest rebuilt kits.

also see http://www.drbig.info/forum/viewtopic.php?f=7&t=2955 and http://www.drbig.info/forum/viewtopic.php?f=6&t=1832
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Re: DR750 Fuel Vacuum pump

Postby Mick75 » Mon Dec 18, 2017 5:49 pm

I'm using a SV650 pump on my '88 750, there was no fuel pump on it when I bought it, when I fitted the SV pump it started flooding through the airbox but a carb rebuild kit solved that problem, I assume that's why the previous owner took the pump off, anyway I got the SV pump in a breakers for €20 and it works fine,you may need to change the fuel lines
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Re: DR750 Fuel Vacuum pump

Postby gadgetboy » Mon Dec 18, 2017 6:09 pm

Thabks both for your speedy response!

I assume that the bike was running well before it was layed up for 5 years so I will most likely go for the replacement sv650 pump as they are much cheaper and readily available! Good to hear that yours is working well with the sv pump fitted.

I believe the sv650 pump has a sprung valve inside which I assume works as a check valve so no concern about fuel flooding when the bikes off and the fuel tap is on?

Final question really aimed at mick75 - what orientation did you mount the pump? Does it matter? I noticed at a stretch the mounting points on the sv pump reach the m6 threaded mounts on the frame, but when I got the bike the pump was only mounted at one of the points, so wondered if this was to position the pump in the correct orientation..

Many thanks!

Matt
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Re: DR750 Fuel Vacuum pump

Postby Mick75 » Mon Dec 18, 2017 7:31 pm

Hi Matt, not too sure about the check valve thing, when I tested it before fitting I found fuel dripped through with the engine off, if your bikes been layed up for a few years you should replace the carb seals, mine is mounted with one bolt into the existing mounting holes and is sturdy enough, can't remember the orientation but I had to fit longer lines to get it to fit
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Re: DR750 Fuel Vacuum pump

Postby gadgetboy » Mon Dec 18, 2017 11:49 pm

Thanks Mick, my previous reply seems to have disappeared, as does your image!

I know what you mean about the carbs flooding petrol into the engine/airbox. Mine did the same when i tried to get it running last week and that was without a pump! So i have taken them out and will give them a strip down tomorrow and get the required parts on order.

The most important parts are presumably the float needle rubbers..
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Re: DR750 Fuel Vacuum pump

Postby ladder106 » Tue Dec 19, 2017 2:42 am

The most important parts are presumably the float needle rubbers..


......and the O-rings under the float valve...and the O-ring under the float "tree"...and the O-ring in the idle mixture screw...and the O-ring under the grey plastic slide ..and the grey plastic slide itself (slide and O-ring available only from BMW from the Funduro and/or KTM dealers)...and the entire float bowl gasket.... and the big diaphragms for the slides.

The carbs are really not fun to remove/reinstall so if you're thinking about doing this at all - do the whole thing.

Standard SR41/2 also use a specific fuel line that is only available from Suzuki to work with the different inside diameters between the carbs and the fuel valve.
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Re: DR750 Fuel Vacuum pump

Postby Mick75 » Tue Dec 19, 2017 10:44 am

I got diaphragms and a carb rebuild kit with all the necessary o-rings and float seals from either Robbinsos or Wemoto, can't remember how much but wasn't too bad, I used the fuel lines off an old jet ski, didn't even notice they were different diameters, bikes running great now
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Re: DR750 Fuel Vacuum pump

Postby gadgetboy » Tue Dec 19, 2017 3:03 pm

Brilliant, i have spoken to Allens Performance regarding the rebuild kit, and all seems to be available for not huge sums of £. They mentioned that big singles usually suffer from the needle jets oval-ing the seats, and the grey slides get damaged towards the bottoms, so i will have a close look at these whilst I am at it. Your images says wemoto on the box, and looking on their site, these are aftermarket kits and seem very reasonable. Its really good to know you have used them with good success, i might very well go this way.

Regards the fuel and breather lines - Is it not possible to just use a single gauge hose? If so, does anyone know what it ID of the hose should be?

Cheers,
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