Archived Posts

[Admin]

not quite finished yet but i will put them on when i do

[Admin]

We like to see the progress of what you are starting with, don't be bashful.

[Admin]

I went for another ride today. The bike definately likes to be reved - over 4,500 rpm it pulls really strongly. Between 1,500 and 3,500 it's a bit hit and miss, it builds revs slowly and needs some clutch slipping. It does n't appear to be misfiring or anything. The gearing is 15/43, it seems like a 14 front sprocket would help.
It could be that the packing that I put in the exhaust baffles is restricting the low speed performance.
I'm also looking for a grey left frame cover, I have a pretty nice blue one that I can trade, or I can buy it.
Some updated before and after pics:

[Admin]

Looks nice! Some of the hop up guys will have to tell you whether the porting and pipes will take away all the low end like you described, but it sounds to me like you have another problem. I would think it might cause it to stumble a little on initial take off, but I would have thought by 3500 it would start pulling. My engine is totally stock and I have a TCE 3into1 chamber and mine pulls light a freight train low and mid range, but the pipe signs off at about 7000.

Wayne

[Admin]

Thanks Wayne,
Yes I think it must be a carb problem, sometimes it seems like it has more bottom end. I think then it is a needle jet issue, as the idle is fine (pilot jet) and the top end is fine (main jet) that leaves the needle jet. I think first I'll take the lazy man's approach and put some gas additive (Seafoam) in the gas tank and ride it around abit.

[Admin]

Rebuilt circuit to fit in a smaller box and did some road testing. Starts fine ,idles good, seems to pull good, no overheating detected. Phil C suggests I road test it for a month before I release the diagram. Cautious testing seems to be a good idea, just to see if it is reliable for the long haul. Will post more when relevant.

[Admin]

Now I don't know how the 500 may differ from my X6, but the ignition switch also plays a part in all this, as there is a cross wire within that is needed to connect the extra charging coils for headlight operation. This wire can fry if the bike is run without a battery, voltage surges across it will melt the solder connection. Worth a check.

[Admin]

Pipes that work well at higher revs will be well out of tune at lower revs, so it's quite normal to lose some low end torque. Lane (Rngdng) has similar pipes plus a port job, so he can tell you what it should be like. And Gordon has/had a set of Jemcos on his GT750.

My RZ350 has pipes on it and there is nothing much but intake noise at lower revs until it gets up above say 4000 and then it comes alive at 7000 and dies at 10,500.

Of course compared to that GSX1100 (if that's what it is) in the background, that GT will always feel rather flat

New exhaust packing shouldn't take away any bottom end power but will keep it quieter.

I'd double check the ignition timing and then start to play with the carbs. Carb settings are more a function of throttle opening than RPM, but are related.

Tell us more about that flat spot. Is the idle OK and if so what about just as you crack the throttle open from standstill or at higher RPM. Does the bike pick up cleanly at small throttle openings at higher revs, or is it still flat. For example, open the throttle to move off with say 2-3000 revs on is it flat? Or running at say 4500 in alow gear close the throttle and crack it open again. Does the bike stumble in both situations or is it OK at higher revs regardless of throttle opening.

I am trying to determine here whether it really is the same RPM regardless of throttle or is it really an issue of which jet/s is/are in play.

For example, wide open throttle uses the main jet from low revs to the redline and beyond, regardless of engine speed. Likewise, the slow jet and cutaway are in play at small throttle openings regardless or engine rpm. the difference is that at higher revs, the extra gas speed will pull more fuel through and may well show up shortcomings that were less apparent at lower revs.

A great tool is to mark your throttle at 1/2 open, 1/4 and 1/8 and then ride at different speeds at different throttle openings. Doing all of this in a safe place and in a safe manner of course.

try 1/8 throttle in say third gear from say 2500 revs and let the motor increase its revs. How did it feel at those different revs. repeat at 1/4 and 1/2 and that will start to separate out the revs from the throttle setting.

My guess is that you have a pipe induced flat area of the powerband that can probably be improved by careful adjustement to carburation.

BTW what carbs are on that bike and what jets are in at the moment?

It could be something as simple as the sides not opening fast enough for some reason - or too fast on those BS40's. If you slip off the air filter, start teh bike and blip the throttle. You should see all 3 slides rising more or less together. Sometimes one is lazy or sticky and doesn't rise until the motor starts to rev. Check the diaphragms and the small holes feeding them.

That's a heck of a clean up job BTW. looks really good now.

teazer

[Admin]

15-43 is what they used in the UK on the M model, versus 16-43 in the US.

Popular opinion at the time was that 15-43 was better than 16-43 on teh street and on the strip ona stock M. Add in more radical ports and pipes and that gearing maybe a little tall.

try a 14 front and see if you like it. Top speed will be limited to about 110, but where I live that isn't an issue

[Admin]

Try this. Disconnect alternator connector. Start bike and run at idle.

Connect voltmeter to alternator side of the connector (set to AC volts) and see what the output is between one charge coil. Raise the revs and see if the voltage rises. repeat for the other coils.

If the alternator voltage is rising, that isn't the problem. With the PEI system, aren't the magnets in the flywheel and don't they charge the ignition system too? If that's right then it can't be the magnets, or else it would not run.

G/W is lighting or night coil and is connected to teh rectifier wwhen teh lights are switched on, R/G is the day charge coil and Y/G is common to both.

For points type pre-PEI, the charge coils work the same way (day/night)but the ignition is powered by the battery, so the fact that it runs is not an indicator of anything. For a points type alternator, remove the stator and use a screwdriver to check for magnetism on the poles of the rotor. If there's enough to feel a reasonable "pull", it should be OK.

[Admin]

Severely retarded timing will do that on a stroker. Combustion is still happening when the piston uncovers the exhaust port and....voila.....blue header pipe. That's what the PO and his buddy did to the #3 pipe on my 550.
I'd still like to wring their stupid necks.....Grrrr.....

[Admin]

Hey TZ375 that's all good stuff. Next time out I'll pay attention to that stuff and mark the throttle openings. The bike idles nicely and will pull away from idle with no problem, then there's a big flat spot until 3,500 when things start to take off. I'm sure some of it is me not being used to the bike.
I just read a (Brit) test of the 750M that says,"What was formerly a tourquey engine is now a revver. Little power is developed below 4,000 rpm, although it will pull usefully for town work. Opening the throttles produces little more than a moan from the air filter, but as the revs build up and reach 4,000 rpm the bike shoots forward and the engine whirrs like a turbine as the maximum power revs at 6,500 rpm are reached."
That sort of sounds like what I have, but mine is more extreme.
BTW unfortunately those are the PO's GSX1100's, I have a more sedate XS1100 as a daily driver, so I am used to plenty of torque.

[Admin]

Try this. Disconnect alternator connector. Start bike and run at idle.

I take it you mean these wires g/w=y/g . r/g =yg
I've got to be carefull here as I've got a electronic ignition(boyer branson) and I don't want to bugger these up.

[Admin]

Johnnie,

Affirmative. I don't know that bike well enough to know if there are two connectors (points and alternator) but in principle, yes. You want to test for output from the alternator without disconnecting the Boyer iggy.

Have you tried to slip the whole stator off its mounts and checking to see if the rotor is still magnetic?

It's unlikely to be the problem, but we are searching for something odd.

[Admin]

CYCLE said

" Unlike the previous LeMans which had usable power from 2000 to 7000rpm, the M model is reluctant to pull the 559 pound package until the tachometer needle reaches 4500 rpm."

So it doesn't make much HP down there, but it should not bog down - just feel a a little flat.