Question about 1987 Suzuki GSX-R 750 H

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What could cause a vacuum in the fuel line?

I cant hold any speed above 70mph. I just recently cleaned the carbs top to bottom, and the previous owner said that they had taken from a later model GSX-R and had just been jetted to be "perfect." But there's always got a big pocket of air in the fuel line. I've got to run the choke for about a minute and a half at 4,000rpm just to make it so that I don't get bogged when I try to throttle hard. I've been told that the petcock may be clogged but I'm not %100 on that. Any help would be great.

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  • Suzuki Master
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I suggest you get your 1987 motorcycle back to original factory specs by your Suzuki dealer for best results.

Posted on Dec 04, 2012

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Posted on Jan 02, 2017

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SOURCE: Suspected problem with choke.

hey apparently and did are two different stories draining the float bowls and cleaning the carbs are two different things the fact that the choke dosent change suggest the carbs are stopped up after sitting for 1 year clean the carbs let them soak in carb cleaner and blow them out with high pressure air, keep notes of the adjustments befor you dissasemble them (air screws)

Posted on Jan 11, 2009

  • 311 Answers

SOURCE: ltz 250 wont idle needs full choke to run.cleaned

hi,sounds to me like the air fuel ratio is all up the ***,locate the air/fuel screw on the carb(normally on the side)screw the screw right in untill it stops,then back the screw out 1.5 turns,this should get the bike to run without the choke,once you have the bike running simply turn the screw in or out untill the bike settles into a nice steady idle,should be good to go,hope this helps...cheers

Posted on Mar 27, 2010

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SOURCE: 2003 Suzuki Volusia 1,600 miles. Runs on choke

do you have a k and n air filter,or the like?

Posted on May 28, 2010

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SOURCE: Hi , my suzuki Bandit GSF 600 2002 plate, off road

Ride the bike 20 or so miles on open road. Stop and remove plug to inspect. 'Are they black or white ?

Black =rich white=lean

Posted on Feb 01, 2011

  • 1 Answer

SOURCE: 2001 marauder I cleaned the carbs & fuel tank.

vz800 marauder hesitates when I Throttle

Posted on Jun 28, 2011

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What could be problem I'm working on Yamaha 660 raptor and it won't take fuel I should say it won't rev up unless I hold my hand over air box restricting air then it is great carbs have been cleaned

Holding your hand over the air box enriches the mixture (choke) you are getting too much air in somewhere (a vacuum leak). Check for leaks at the boots between the carbs and the head. Also replace any vacuum lines that are broken or cracked. (Cracked vacuum lines won't usually cause severe problems if the lines are small, but they will cause your engine to run lean and that's not good.)

Jan 28, 2016 | Yamaha Motorcycles

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I have a 2009 yamaha r6 and it recently started shutting off on me. I was on the freeway doing a steady 70mph and my bike turned off. Any advice?

Remove the fuel "turncock" from the bottom of the gas tank. I'll bet you'll find that it's full of gunk and debris. What I did was clean it out with carb cleaner then removed the fuel tank, emptied it except for about a cup of gasoline. Then I put about 6 small nuts and bolts in it and shook it around really well. The nuts and bolts knocked all kids of debris loose from the bottom of the tank. I then removed the nuts and bolts, put the fuel line back on and she started right up! Hope thus helps.

Jun 08, 2014 | Motorcycles

1 Answer

Why does a carbureted motor run fine at cruising speeds, and cold starts but at warm idles and coming to a stop sometimes shuts off and idle surges?

Maybe float level is low. If possible split top off carb to observe wet level inside carb. Thinking 2 things for deceleration that changes pressure in fuel line is volume push by fuel towards front components and maybe Evaporative Emissions is getting solid fuel instead of vapors from splash.

Idle dashpot is part on some early carbs to allow throttle gradual closing. Some are vacuum controlled with what is called a "vacuum tree" which routes the vacuum to the dashpot by temperature. Vacuum tree could have wrong hose routing or THERMOSTAT for engine could be too cold.

Mar 03, 2014 | Ford Festiva Cars & Trucks

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2005 Harley Sportster 1200 Custom stalls at highway speeds

The diaphragm petcock operates by vacuum.
Sometimes, the vacuum line comes unhooked, cracked or broken.

Check the vacuum line.

Also, the diaphragm petcock sometimes dies, and needs replacing.

The reserve DOESN'T operate by vacuum.

Feb 12, 2014 | 2005 Harley Davidson XL 1200 C Sportster...

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Blower is stalling out at high power.

Hi and welcome to FixYa, I am Kelly

Stalling at high speeds is caused by fuel starvation.

Causes for fuel starvation are:
1. Pin hole in the Primer Bulb (Item 3) this link: PN: 12538108660

2. Fuel filter in gas tank is clogged. (Item 5) this link:

3. Fuel lines damaged or cracked (Items 7 - 11) above link

4. Missing gas cap vent (Vapor lock) Items 15, 16 of # 2 link above

5. Diaphragm / gasket / float needle problem inside carb. (Carb service manual below see page 7)

The gasket / diaphragm kit that usually corrects this is item 34 this link:

I doubt that making fuel mixture adjustments is going to correct the symptom you have.

- Your going to have to check fuel flow from the fuel tank to the carb connection.
- Check for any loose screws on the top and bottom of the carb (tighten and test)
- Dis-assemble, clean with carb cleaner, reassemble & test
- Replace gaskets and Diaphragm making sure float metering needle is clean

Hopefully with this information you can isolate and repair the problem.

Thanks for choosing FixYa,

Sep 02, 2011 | Echo Gas Blower 185 MPH 900 CFM Blower...

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Hello. I have a 1999 Suzuki Intruder VS1400. Used fairly regularly, but by no means every day. Recently bike is stalling at low speeds, seemingly not as a result of the idle setting, which is fully turned...

It sounds like its time to have the carbuerator cleaned more then likely you have some varnish build up in the idle circuit. I cant remember if that bike has a fuel filter in line from the tank but if it does I would recommend changing that first as it could simply be starving the motor of fuel at idle.

Apr 11, 2011 | 2003 Suzuki VS 1400 Intruder

1 Answer

Mower will not run in high speed idles at one speed push throttle it runs at the same speed then stalls out whith lots of gas in the carb

Your carbs main jet is most likely blocked. When the throttle goes off the idle jet to the main jet there isnt enough fuel flow and the engine stalls.

You need to removed the main jet and run a small piece of wire through the main jet to clear it. This is a good time to look at the inside of the float bowl to see if you have excessive water, rust or dirt accumulating that is a sign you should clean and drain the fuel tank and lines as well. The main jet is actually the bolt that holds the fuel bowl on the bottom of the carb! You need to look very close at the jet near the top of the threads to see the little whole there and clean it. A wire brush to clean off the threads and fine piece of wire strand to clean the hole will do the trick!

If you dont have a bowl type carb you will need to remove the carb from the fuel tank and locate and clean the inlet screen and main jet and then remove the fuel tank and clean it out too.

Good luck and be careful.

Jul 16, 2010 | Briggs & Stratton Garden

1 Answer

1987 GPX (ninja) 750R. It has tons of get up and go on the flat roads and going down hill. However when you start to go up a hill or incline it dies. Recently rebuilt the fuel tap but the fuel is flowing....

hi,this might help,you will have to remove the carbs to do it,but check the float levels in the carbs,it sounds like it is not getting enough fuel when the load goes on,the engine is using more fuel  under load and the carbs  cant keep up,while you have them apart give them a good clean out,make sure all the jets are nice and clean,also have a look at the air filter ,a blocked or dirty air filter will also affect top end or"under load"performance,before i forget,when you had the fuel tap apart did you make sure that the gauze filters on the petcock were nice and clean,if they are just slightly dirty they will also affect performance.if the bike has a vacuum pump on the fuel tap,check that the vacuum line from the pump to the pickup point(normally the intake manifold or a point on the vacuum side of the carbs,ie engine side)is in good condition with no kinks or cracks,if it has a kink in the line it will not create enough vacuum to run the pump,causing poor fuel flow  under load,i have just done a repair on an 89 gsxr 750 slingshot that the owner has spent a fortune on trying to get it right,and it turned out to be a $4.00 kinked vacuum line to the fuel pump...hope this helps...cheers

Mar 25, 2010 | 1987 kawasaki GPX 750 R

2 Answers

No full speed then dies

Fuel starvation - 'lean fuel' condition
Basic things to check:
1) spark plug
2) spark arrestor in muffler
3) fuel lines and tank filter
4) turn adjustment needles out (counterclockwise) 1/4 to 1/2 turn
Chain Saws:
5) check impulse tube and intake boot for cracks or leaks
*if all of the above are OK and/or do not improve performance then:
Remove Carburetor
6) replace gaskets/diaphragms
a) use a spray carb cleaner to clean jets, holes, and body of carb
b) fuel pump diaphragm goes against the carb body,
then the gasket towards the outside
c) metering gasket goes against the carb body,
and the diaphragm goes towards the outside

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1 Answer

Missing Fuel Lines

the 2 spigots between the 1st & 2nd carbs are for the 2 vent hoses.the 4 skinny hoses on the bottom of each carb. are for carb. bowl overflow.

Feb 17, 2009 | 1988 Yamaha XJ 900 F

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