cuts out bad on topend??

[400man]

recently got a 87 250r the other day, a clean mostly original bike with a few extras. I dont know to many details on the motor other than its got a coolhead with 210 psi, fresh wiseco 68mm piston, stock port cylinder, fmf fatty exhaust, and im pretty sure its a 38mm air stryker carb. I havent took the carb bowl off yet, just the drain plug to change out the main jet. started with a 170, went up to a 180, then down to a 160, still acts the same on topend with each jet, mayble a little worse with the 160. its cutting out bad at WOT in the higher rpms. it has a really strong bottom end and midrange pull that comes on really early in the revs. im running 110 race fuel with belray mc-1 mixed 40:1 currently.

I called a local shop and they said its probably electrical, like the coil or the stator. I have not checked behind the stator cover yet so im not sure if my problem is hiding in there or not. any advice on what to try first?

[J.B.]

While checking electrical, check your grounds.

[skyhighatv]

try gapping your plug down to .018 sometimes they like that w higher compresion.

Jaysin

[machwon]

As Jaysin said, gap the plug at .020 (that's what I use) and start with a fresh plug. Probably going to need between a 178 and 185 main.

[400man]

I completely forgot about spark plug gap :o . well I checked the plug and it was like .035. I gapped it down to .020, but it still acts the same....cuts out and sputters at wide open throttle. it had a b7es, I tried both that and a b8es and they act the same. its got a 170 main, but the next biggest jet size I got is a 172, then a 180. would it change anything if I messed with the needle?

[k7mm]

Yes at wide open throttle you are into the main jet,so that is a good place to start.But it sounds like you've been up and down with the mains and it's made no difference.I would take your carb off and totally clean it,just so that you can be sure that it is not the carb.At wide open throttle is when you have the most load on your engine and therefore if you have a air leak that is when the engine will suck the air in and break up.You can get a good compression reading and still have an air leak.You talked about taking the stator cover off.Take the cover off and look for oil inside the case.If there is any,then your crank seal is bad and therefore sucking air at wide open throttle.Also check that your counter balancer holder is intack,sometimes they will crack where they hold the stator pick up.You can eliminate two birds by taking that side cover off!
Keith
P.S. You should be running the br8 or 9es not the b8 or 9es plugs.

[400man]

well I took the bike out in my trails near the house to do some test riding.....its acting even worse now and cuts out bad at anything past 1/4 throttle..

so I ride back to the shop and next I took the carb apart and cleaned everything, blew air through every hole in it, has a 55 pilot, needle is on the middle clip, and a 170 main. put the carb back on.....runs same as before.

next up is the stator cover, popped it off and it about made me gag with what was in there.... I should have snapped a pic to post on here :blah: . it had some nasty light brown muddy water in there and the stator and flywheel and everything was light chocolate colored. ive only seen one other bike worse than this, and that was a banshee that had a bad stator cover gasket and it was coated completely in rust. but anyways, I cleaned up everything in there, shined up the flywheel with a wire wheel, got everything back to how it should look normally. the counter balancer holder looked fine and theres not any sign of a oil leak there. put everything back together and it still runs the same.....:confused:

so what should I try next, a new coil maybe??

[k7mm]

Is that nipple on the stator pick up ground down flush?With all that mud and dirt in there it could have ground down that nipple to nothing,and that could be your problem.I'm talking about the black pick up.The nipple sticking out of it.

[wilkin250r]

It's beginning to sound more and more like it's ignition-related. Unfortunately, it's very difficult to diagnose exactly which component. I've heard of other people having this exact problem and the culprit was the CDI, and other times (same symptoms) the problem was the flywheel, and yet another time the problem was the wiring harness and poor connections.

I wish I could pinpoint you closer, I really do. The REAL problem is that the stock ignition gets weaker in the higher revs, so any little problem is enough to push it from barely functional into non-functional. So which little problem is it? Unfortunately there are plenty to choose from.

[wilkin250r]

In fact, I'm facing this exact same issue right now, but the problem doesn't look like it's the CDI or the coil. But I won't be able to tell you any further, because I'm just upgrading the entire ignition to a CR250 ignition. It's a little spendy for some, I know, but it's almost guaranteed to fix your problem.

Unless your problem is an air leak, as someone already suggested. But I've already ruled that out of my problem.

[latheboy]

Wilkin-- One of those junk stators I sent you made my quad act like this. It would start reasonably easy, and idle all day. But the spark was so erratic and weak, that when I gave it fuel and air (mashing on throttle) the spark was blown out. I replaced the stator and all was well. The old stator ohm tested ok and produced some spark, but it was weak and inconsistent.

[wilkin250r]

I'll keep an eye out for it when I actually start the testing. It will be handy to know what kind of factors would cause that.

Right off hand, I'd say most likely a bad connection, and it doesn't necessarily need to be at the "connector". It could be a bad solder joint on the stator itself, or on the pulse generator.

[DnB_racing]

Originally posted by wilkin250r
I'll keep an eye out for it when I actually start the testing. It will be handy to know what kind of factors would cause that.

Right off hand, I'd say most likely a bad connection, and it doesn't necessarily need to be at the "connector". It could be a bad solder joint on the stator itself, or on the pulse generator. wilkin250r what type of readings should I be looking for if I was to hipot my stator, and what are the limits I should go to?? and if I was to megg it would that even be worth it?

[wilkin250r]

You're probably not going to get anything from a hipot test.

For those that don't know, a high potential test is basically a test of insulation, you apply a really high voltage (like 1500 volts or so) between the windings and the chassis to make sure the insulation is good and it's not leaking power to ground.

However, on a 250r stator, the chassis IS ground, you don't have any actual isolation there. You wouldn't be able to hipot test it without desoldering the ground connection.

[DnB_racing]

Ive got access to all kinds of testers which one would be able to test the integrity of the windings???basically which type would show if there are any issues at different rpms or voltages????

[wilkin250r]

Originally posted by DnB_racing
Ive got access to all kinds of testers which one would be able to test the integrity of the windings???basically which type would show if there are any issues at different rpms????

Excellent question. I wish I had an answer for you, but at the moment, I can't think of any test, without actually spinning the flywheel around it and testing it under load.

The issue I'm looking at is the stator is actually a really simple mechanism. It's just a coil of wire, and an iron core. What could go wrong? If the insulation on the wire was melted and the individual windings were shorted together, that would show up on a resistance test. Likewise, if the wire was broken, that would also show up on a resistance test.

The only thing I can think is an inductance test, and a more sensitive and accurate resistance test (something that can measure in the milliohms within 1% accuracy).

[DnB_racing]

Originally posted by wilkin250r
Excellent question. I wish I had an answer for you, but at the moment, I can't think of any test, without actually spinning the flywheel around it and testing it under load.

The issue I'm looking at is the stator is actually a really simple mechanism. It's just a coil of wire, and an iron core. What could go wrong? If the insulation on the wire was melted and the individual windings were shorted together, that would show up on a resistance test. Likewise, if the wire was broken, that would also show up on a resistance test.

The only thing I can think is an inductance test, and a more sensitive and accurate resistance test (something that can measure in the milliohms within 1% accuracy). something like a dobble?

[wilkin250r]

Originally posted by DnB_racing
something like a dobble?

I'm not familiar with that one...

[DnB_racing]

we use it to test transformer windings and motor windings,
I dont do much of the testing but im going to ask our EE"s about this and try to figure out which test would be able to track if a winding is degrading whether it be through insulation brake down or a resistance problem

we must have something at work to check it
I work at a power plant and we test everything

I spelled it wrong its doble, this method of testing insulation or insulation systems uses A.C. voltage to measure loss in watts.

[wilkin250r]

I am totally behind this!

I've done lots of transformer testing ( I used to design small transformers and inductors, like less than 100 watts) but all my insulation tests were from one winding to another. I don't know how to test the insulation on a single winding.

But talk to your EEs, I don't know everything. If you find a useful test, clue me in, I'm totally willing to learn.

[DnB_racing]

it will be a couple weeks as im out now on medical ( I had a stint placed and ill be out for a little while) but we have testers for everything there must be one that will show something useful i will definitely find out!!

[wilkin250r]

Originally posted by DnB_racing
it will be a couple weeks as im out now on medical ( I had a stint placed and ill be out for a little while) but we have testers for everything there must be one that will show something useful i will definitely find out!!

I'll remind you. :devil:

[400man]

wow I appreciate all the replies. I cant say I know much about ignitions and electronics......like the last several posts above.

so would the stator be a good place to start for me?

[wilkin250r]

Originally posted by wilkin250r
In fact, I'm facing this exact same issue right now, but the problem doesn't look like it's the CDI or the coil. But I won't be able to tell you any further,

I don't know if you've solved your issue or not, but I'll update you on mine, it might help you out.

My flywheel was bad. I pulled it off to install the CR250 ignition, and I gave my flywheel a good shake, and it rattles pretty bad. The magnets inside are all broken (somebody probably dropped it).

I would suggest to you that you go through the normal resistance checks on your stator, because that's easiest, then I would suggest pulling off your flywheel and giving it a good shake and listen to it, see if it rattles.

[latheboy]

...and if anyone needs a stock flywheel, I have two of them for sale. LOL!

[400man]

ok so I tried a different stator, got it off ebay and it looks 10x cleaner than the one on the bike. didnt change anything at all and still cuts out bad once the revs start climbing into the midrange. also my flywheel is fine, not loose at the rivits or anything. I did check all the conections and grounds and didnt raelly see anything bad. I guess the next thing im gonna try is a coil.

but on a side note, could it possibly be the fuel that I put in it? its got 110 race fuel with belray mc-1 at 40:1 right now. the fuel that the previous owner had in it was just pump gas with the same oil. I changed over to the race fuel when I first checked the compression at home (forgot and left the tester at the shop when I went and looked at the bike) and seen it had about 210 psi. when I test rode the bike at the guys house, it ran great except for a small miss/cutout in the high rpms when I wound out each gear, kinda felt lean I guess and I could also hear a small bit of spark nock in the topend.... but since I have put the 110 in it, its been acting up like I described above.

[wilkin250r]

How old is this race fuel you're putting in it?

[machwon]

Connectors, new spark plug, then jetting. electrical componenets usually either spark or they dont, same with fuel. New spark plugs that work for a while then start missing means it's jetting.

[400man]

Originally posted by machwon
Connectors, new spark plug, then jetting. electrical componenets usually either spark or they dont, same with fuel. New spark plugs that work for a while then start missing means it's jetting.

I mixed up some fresh pump gas and 40:1 premix and it still acts the same, so I know the race fuel is ok. also installed a brand new spark plug but didnt help anything. the spark looks kinda weak when I tested it against the cylinder head. so I guess im gonna try a new coil.

[400man]

problem is solved finally :blah: . bought a new coil off ebay for 25$ http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=270718783139&viewitem=&sspagename=STRK%3AMEWAX%3AIT

hooked it up and took it for a ride. runs like a top. this thing pulls hard from midrange and beyond....:)
just now I need to do a plug test and get my main jet right before I do any long WOT hauls across the field.

[jcs003]

Originally posted by 400man
problem is solved finally :blah: . bought a new coil off ebay for 25$ http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=270718783139&viewitem=&sspagename=STRK%3AMEWAX%3AIT

hooked it up and took it for a ride. runs like a top. this thing pulls hard from midrange and beyond....:)
just now I need to do a plug test and get my main jet right before I do any long WOT hauls across the field.

thats what happened with mine. went nuts trying to find my problem and there was some of the insulation stripped off my coil wire. dont know how it happened but i found it. funny thing. i spend $600 on a cr250 ignition, then find my bad coil wire. anyways, im glad i got the cr250 ignition. effin awesome upgrade.