Got a 1988 ex500 with a little under 21k on the clock.... Bought it partially working. the bike will start and will idle/runn at the lower end of the tach but once you give it throttle it cant make it past about 3.5-5k... ith full throttle it will just bogdown to about 2k and bouce to 2.5 and back.

Here is a video

Previous owener replaced the carbs (i inspectec and they look good and clean) I noticed the clymer said the jet sizes were supposed to be 130 and 35 but the one in the removed carbs (i have two sets) was a 120 i believe. any idea's? know what yours are? it at one point ran on these.

tested the coils (tested good)

Pickups test good

IC was replaced with a used one but i'm not sure of a method to test (does spark though... pulled and grounded plug)

Replaced plugs (gapped to .64mm) and snipped and rescrewed plug caps

Tried running open airbox (no luck)

Going to do a compression test today and if good going to do the valves (clearances)

So what do you guys think? a little extra info, california emissions model (canister removed) and the tank vents just fine. tested fuel flow with another tank and its good. rubber on the carbs looks OK to me. There is a 2 to 1 exaust on and it sounds gutted but i still dont think it should be this bad.

If anyone knows how to test the IC unit with a multimeter or something let me know. think a dealer could check one for me? Or does anyone in the NJ tri state area have one that i could bolt on for a couple of mininutes to rule out the problem? Thanks fellas.

 

I wouldn't think the jet size could make that big of difference that the engine couldn't get past 5k. Did you actually take apart the carbs yourself and inspect them? Could the choke be stuck? maybe the diaphram for the needle on the top of the carb(s) are torn. You need to take a good close look at the carbs. also check for any air leaks on the intake boots.

 

ok the carbs i almost ruled out but im gonna reclean and inspect my old set (which are in grat shape wear wise) and put those on and recheck the boots.... i did check the diaphrams on both sets of carbs and they seem good but no harm in checking again.

still gonna do a compression check and valves cause they are overdue.

one thing i noticed is that the prev owner had a K&N filter installed and may have overoiled... going to hit it with the air compressor and get rid of some of the excess stuff... maybe its gettin in there and gumming stuff up.

thanks for the help...markmeinteil i'll give you an update tonight after i get something accomplished after work.

 

Dang man, you're a very detailed guy with all your pics and video!

I have a few questions for you. Did you take "both" the primary and secondary jets out to inspect?

When you pull the throttle wide open, did you get any dark smoke coming out of the exhaust?

I watched your video several times. About midway through, when your bike was revving up and down, was that you doing that? I didn't notice your hand moving much at all while the throttle was jumping all over the place.

Last of all, have you checked your choke cable to see whether or not it completely opens the butterfly valves when the choke lever is pushed all the way forward? It might be a long shot, but maybe the choke is not disengaging completely, therefore starving your engine of air.

 

Ok, I watched that vid again.[&:] While listening to your engine as it gradually builds up rpm, I can just tell something about the way it's firing isn't right. Like I said above, it could be getting choked out, but if thats not it, I think somewhere in your ignition is acting up. Are the wires good? you may want to check them out. (ohm them for resistance) I don't know what their ohm rating/per foot would be, but find out and check them. When you said the coils checked good, did you just check if they were firing, or did you check the electrical resistance on them?

just throwing out ideas here, hopefully one of them will work[sm=smiley20.gif]

 

haha yeah i been posting on a few forums... in order to get everyone up to speed i just was thorough...

tore down the old carbs last night cleaned the **** outta everything and adjusted the floats to 17mm (were a bit off)
removed the current carbs and installed those (i'll test it after work cause i finished at like 1am fingers crossed) fuel/air 2.25 revolutions out. bladders are good

Chokes seem to be closeing enough i cant physically push them anymore. and the boots look great... if this all doesnt work im gonna take the airbox apart and look for cracks etc...

I did the valves so they are all in spec and i can run a compression test today and be able to tell whether my rigs or valves are bad. (dropped a bolt down the timing chain and one in the block thru the coolant hose openeing...sigh setbacks... thank god for magnets and aluminum engines)

I had run the starter with one plug out and grounded to the engine and saw a spark but i suppose i should get a timing light or something to see if its still working at higher RPM's (new gapped plugs). the only think i dont kno is what the resistence of the wire itself is supposed to be... i cleaned the caps... snipped the plug end and rescrewed etc. What color are the wires that go to your coils? my one side is green and red and the other is red and black but the tabs on the coils are green and black... leads me to believe that perhaps someone did their own wiring job. perhaps something to look into. (resistance checked ok/ within spec.)

At the end of the vid where it was jumping that was just holding about 3/4 throttle... i'll make a clearer vid today (unless the thing just runs then i'll spend the rest of my day at the DMV)


you know how to test the ignighter? like with a multimeter? think a kawi dealer would have a tester i could plug it into if i brought the unit in? i have 2 ( prev owner replaced but prob with a used one)... is perhaps anyone here in the NJ/NY area that could drive by and let me borro their Ic for like 15 min so i could eliminate the possibility? im gonna bolt on the old one today to to test it out....

ideas?

Again thanks for reading... i'll keep you up to date

 

I'm not completely sure about testing the igniter. As far as i'm concerned, you would need a special module tester that probably the dealer would have. The way the throttle bounces all over the place, I think you may be heading in the right place with the igniter. I might be wrong, but I would think the igniter would have several RPM circuits the way cars do. (different circuits in the module control different RPM ranges) Just a guess. It's almost like it cuts off ignition after it hits a certain peak.

 

So, have you figured anything out yet?

I let three mechanical technicians watch your video at work today. 2 of 3 said there is almost no shadow of a doubt that it can only be a air/fuel related problem. The other guy just said get a new bike, so he doesn't count.

Trieu, our top technician right away pointed out there is nothing wrong with your ignition, or timing. If there was, the bike would be hiccuping, and backfiring. "don't even bother testing the ignition components because you won't find anything wrong" he said. (trust me, this guy is unbelievably good with engines of all types.)

There are two things to check: while running use a can of ether and spray around the carburetor body, and intake boots. Anywhere that outside air could get in besides the air cleaner. If the idle changes, you have a vacuum leak. I don't think you'll see any results doing this. The idea I came up with just dawned on me. This is a theory that I came up with:

On your carbs, you have two vacuum nipples up top right? (one on top of each barrel) One side should have a line that goes to the gas tank's petcock. While your engine is running, the vacuum in this line pulls on a diaphram in your petcock that in turn allows gas to flow out of the petcock to feed the engine. (still reading me here?) The other vacuum nipple may have a cap on it, or has a line that goes somewhere else. (this line doesn't matter for where I'm going on this topic)

If your petcock valve has a prime selector on it, try running your engine with the petcock on prime. Doing so, bypasses the diaphram in the petcock that normally stops the gas from flowing when the engine is shut off.

More than likely, the petcock on your gastank only has "off", "on", and "reserve". if this is the case, you will have to use a seperate container such as a gas can. Run a 5/16 fuel line with a male to male coupler at the other end to plug into your bike's fuel line. Make sure you cap off the vacuum port on the carb that goes to the petcock. Start the engine up and let it run for a minute. with any luck, the engine won't have any problem revving up, and won't cut out like it was before.

My theory is that either the vacuum line leading up to the petcock, or the petcock itself is starving the engine. since the petcock needs vacuum to let gas flow, the petcock's diaphram might be leaking vacuum, which shuts off the gas to the engine temporarily starving it of gas until the engine's revs go back down to idle. (you have much more vacuum at idle, than at full throttle) If this works, buy a petcock rebuild kit, and a new vacuum line.

Hope you understood me there. LOL I hope it works.

 

haha sorry i took so long to get back.... Got it all figured out... after doing almost every maintenance possible it ended up being an airbox leak as i suspected towards the end. On the CA model the breather for the carb float bowls is routed back into the airbox via hose. i yanked it and stuck my finger into the airbox hole and walla! revvs like a monster. repacked my muffler (still to loud for my tasts) and filled er up. runnin good... got some rust in the gas tank to get rid of but im ordering kreem as we speak. inline filter for now... i think the petcock is getting plugged up cause it died after about a half hour of riding on the highway... stopped shook it up and let it sit a few and it wwas all gravy... losing power on the highway sucks...

thanks for all the help... you all had the right idea and those were pretty good strategies... i just got lucky... glad i did before i spent wadds of cash... only spent about 70 all together. (hose,filter,carb cleaner, contact cleaner, new chain (for a piece on mind), oil and oil filter)

your an asset to the forum. usually people dont have enough motivation to follow through witha post

-Edward A Lucas

 

Glad to hear you got everything fixed up Quickstreek!

[sm=smiley32.gif] to markmeinteil for helping out!





*You will find that pretty much everyone on this forum is just like mark - always willing to lend an helping hand when they can! That's what makes things so great here!*