GSX750ESD Is Going To Burn

[Dak S83]

I'm about to set fire to this damn thing, carbs all back and bike all back together and what do ya know, it wont frickin spark again. It's back to the randowm spark thing when you let go of the starter button. It MUST be the right hand switch gear, cant pull the switch completely apart as far as the contacts so if anyone has one to suit lemme know. Today I'm going to hot wire it bypassing the kill switch and if that doesn't work its getting a match.

[Laava]

When I rebuilt my gsxr750, I could not get it to run and it was the coils. There are two of them and when they were tested on a coil testing machine they were absolutely fine. But they would not work on the bike. If you have similar, ie, two spark plug leads from each coil, try testing them with an ohmeter. You are essentially testing for continuity. So if the needle swings way up the gauge, the continuity is good, but if the needle barely moves this is because the windings of the coil have a break at some point and although a coil testing machine can make the coil spark, bridging the internal break, they will not work on the bike. Just my 2c.

[sidecar bob]

Im in town today. Will drop around sometime to pick up my box & have a tinker on it with you for a while.
If you want to have a fire i will bring a pile of cardboard for you to burn & take the bike away.
Same result.<_<
I have a switch but not with me.

[Dak S83]

Cheers mate, yup it definatly the switch gear. Had a go at cleaning it again and it fired up. BUT, the bloody thing, despite having the carbs done by a shop, and I had a quick look before putting them back on, the bloody thing is only idling on 3, no 2 is out, when ridden though it comes on 4, I think, hard to tell but it goes bloody good. I'll be around, gimme a text.

[husaberg]

As an aside to the electrical problems.
What kind of fuel taps do that era have?were they still the vacuum ones then?
Also the carbs might have been cleaned but is the tank?

[Dak S83]

As an aside to the electrical problems.
What kind of fuel taps do that era have?were they still the vacuum ones then?
Also the carbs might have been cleaned but is the tank?

Copy that, yea vacuum tap, it definitely getting fuel to all four carbs. Tested the tap and it's all good and flushed the tank. Seems maybe the guy that cleaned the carbs for me may of missed something in the pilot circuit on number 2. It does seem to run fine at faster speeds and load. Gonna try and take it for a good ride and check exhaust header temps just to make sure it not lean at higher speeds with some Redline cleaner in the tank and see what happens. Failing all else it's out with the carbs again.

[SaferRides]

Probably a dumb question, but are the HT leads OK?

[Dak S83]

Probably a dumb question, but are the HT leads OK?

Roger that, have had success. It was the bloody kill switch all along, it was still working but must of had high resistance and killing power to the coils and igniter while you were winding it over. Just got the carb problem to sort now, despite having them professionally cleaned number 2 has no fuel at idle and just off throttle, pilot system must have a blockage so its out with the carbs again damn it. And yup, it must be the carb, it has spark and plenty of compression on 2 and runs well at cruising speed and when accelerating and there is no vacuum leaks.

[mulletman]

I'm about to set fire to this damn thing, carbs all back and bike all back together and what do ya know, it wont frickin spark again. It's back to the randowm spark thing when you let go of the starter button. It MUST be the right hand switch gear, cant pull the switch completely apart as far as the contacts so if anyone has one to suit lemme know. Today I'm going to hot wire it bypassing the kill switch and if that doesn't work its getting a match.

Would've made a good Cold Kiwi hack and burn...when running

[neels]

Roger that, have had success. It was the bloody kill switch all along, it was still working but must of had high resistance and killing power to the coils and igniter while you were winding it over. Just got the carb problem to sort now, despite having them professionally cleaned number 2 has no fuel at idle and just off throttle, pilot system must have a blockage so its out with the carbs again damn it. And yup, it must be the carb, it has spark and plenty of compression on 2 and runs well at cruising speed and when accelerating and there is no vacuum leaks.
I had a similar problem with a bike a while back, it turned out to be the choke lever on one of the carbs was slightly bent, causing one cylinder to run rich and drop out at idle, normal running speed it was fine. Might be worth a quick look before you dismember it all again, pulling carbs off is a pain in the arse.

[F5 Dave]

Old petrol blocked carbs are a swine. Do check the choke ccts as well, those tubes into the bowls need to flow and there needs to be connection right up to where the chokes seal off. I needed to run a 0.3mm drill through some. Pipes stayed cold on some until warm enough not to need choke and choke was working on some cylinders so they worked proper.

Then I found the fuel hose kinked when tank on. In line Filters cause kinks.
Missing vacuum take offs can catch you. I had some carbs from another bike vs gravity tap on this one.

Suzuki tanks of the era just love to rust inside and the silt gets everywhere.

[Dak S83]

Well, touch wood its all good now. Cleaned out number 2 carb again, the cheats way, took the top off and the slide out, removed mixture screw and then blew cleaner and air through the main and the idle screw hole. This thing really had me going, in the end, apart from dirty carbs from sitting, the main problem all along has been the starter motor. Although it spins fast enough it must be worn or dirty enough to draw too much current from the new battery and making the voltage to the igniter and coils drop to about 9.2V while cranking, not enough for the coils and/or igniter. Had it on charge all night and it started first pop this morning. Took it for a 250km blat today and it runs very well. Will need a sync and idle screw adjust to get it a bit smoother but so far now all is good. Thanks to all for the hints and tips, special thanks to sidecar bob for the loaner igniter for testing and the visit the other day, much appreciated.

[sidecar bob]

With the starter motor, obviously clean it out & lubricate the bushes, but a lot of current draw seems to come from brush material jammed in the grooves of the commutator.
Run a sharp scriber up the grooves to remove the copper dust that accumulates.
Also clean up the commutator with 600 grit wet & dry paper, & wash it with brakleen.

[Drew]

Also clean up the commutator with 600 grit wet & dry paper, & wash it with brakleen.

Hmmm, another dude who I trust has steered me very clear of cleaning the contacts that the brushes run on. He says clean everything else, but leave the coppery goo on there as it serves to lube the mating surfaces.

[sidecar bob]

Hmmm, another dude who I trust has steered me very clear of cleaning the contacts that the brushes run on. He says clean everything else, but leave the coppery goo on there as it serves to lube the mating surfaces.

He may well be correct, but you should hear the starter on my M535i since it got all I described.:gob:
I only meant a few rotates with wet & dry in your hand.
What happens when you machine a new surface on the com?

[jellywrestler]

Hmmm, another dude who I trust has steered me very clear of cleaning the contacts that the brushes run on. He says clean everything else, but leave the coppery goo on there as it serves to lube the mating surfaces.

all that does is burr over until there's enough to short out to the next comutator bar and then it's meltdown time. i clean them in a lathe, clean the grooves out, then use commutator stone to bed the brushes into the surface.

[Dak S83]

Well, I give up, nothing seems to fix this damn thing. Pulled the starter today, it was in remarkably mint condition considering its age. But anyway, cleaned it all up, check the armature for shorts etc, nothing found, gaps were all good, brushes well within spec so cleaned everything, lubed etc and put it back in. Also now have another brand new battery. The BLOODY thing will STILL not start under it's own power, if I jump it off a running vehicle, my 4WD, it fires up fine, also when it's warm it will fire up fine all by it's own, easier to start when it warms with less draw probably. Got me beat, short of replacing the starter and starter relay etc with brand new parts I'll be buggered if I know. Might be time to wire in a relay to feed the igniter and coils so bypassing all the switch gear to minimise voltage losses.

[FJRider]

I used to have an old XJ750. The compression was down. It was a bitch to start off the starter motor but would bump start first go when you released the clutch. If it was left after running it would start easily on the same day on the starter ...

[SaferRides]

Might be time to wire in a relay to feed the igniter and coils so bypassing all the switch gear to minimise voltage losses.
Could be worth a try. The R1 has about 1.5 V of voltage drop from the battery to the coils. I tried a set of stick coils last year, and it was a pain to start and would cut out now and then when it was cold. Absolutely fine once up to temperature, and fired almost instantly.

I was going to fit a relay to feed the stick coils, but it ran well with the standard coils and I was a bit concerned about damaging the igniter. I may yet try it though, as it runs so nicely on the stick coils once up to temperature. .