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ENG243

1994 Kawasaki Bayou 400 power loss

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Hello 

I have a 1994 Kawi Bayou 400 which had been running well until it sat for about a month. I left the carb dry while it was park and the temp had dropped below 0C in this time. Pulled it out last night to go for a ride and it fired up just like it should but noticed when I started to head down the road I could hold it to the bar and it didn't seem to accelerate. Lower gears weren't as noticeable but 4th and 5th it just seemed to have no acceleration and half or full throttle  made no difference. if I tried to go into 5th gear with any throttle it would stall. I turned around and just poked home very slow and it seemed to stay running but this was between 15 and 20 km/h max. 

I have taken the carb apart and it appears to be clean and nothing stood out on inspection to have dirt or ice. Is there something I should dig more into? 

I have checked the plug and it appears to be sooty with easily rubbed off carbon. I plan to get a new plug today and test. 

compression with the throttle wide open is 175 psi. 

I have opened the drain plug in the exhaust thinking there could be a mouse in the exhaust or something but no difference. 

I do find the engine is tickity compared to my 2000 Honda but I am not sure if this is just me looking for issues or if it has always been this way. 

If anyone has any insight I would appreciate it.

In the last 6 months I have done new oil and filter ( mystik synthetic) 

new Peak RPM CDI 

I have noticed the fan comes on more often with the new CDI, could this be a program thing?

 

Mike

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Have you checked the aircleaner. Here in NZ we get high humidity and paper filters get moist and block up.. Probably not a problem there with ice I guess.

If the new cdi was making it run a bit retarded it would get hot..  Probably shouldn't make the plug black though.. not unless it was miles out of time..  If you have the old cdi still you could swap it back and try.

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On 12/27/2020 at 11:56 PM, Mech said:

Have you checked the aircleaner. Here in NZ we get high humidity and paper filters get moist and block up.. Probably not a problem there with ice I guess.

If the new cdi was making it run a bit retarded it would get hot..  Probably shouldn't make the plug black though.. not unless it was miles out of time..  If you have the old cdi still you could sbvap it back and try.

Hey thank you for the reply. I have removed the air cleaner completely to be sure there were no restrictions and I have opened the drain in the muffler incase is was an exhaust restriction. Neither have made a difference. As for the old CDI the reason I swapped it out was I lost spark in the spring out of the blue. I tested all the components in the ignition system and came to a bad CDI. I put the new one in and it fired right up and ran like a top. The only thing I noticed it the fan seemed to come on always but I couldn't remember if this was normal or new. 

New update is I have tried a new CDI with the same results. This is the same brand as I was already using. 

When running in 1st gear it will hit a rev limit, second same thing but seeming under power and then 3rd and 4th you can hold it to the bar and it seems to hold or drop some but doesn't seem to miss and go like a limiter. 

My last idea would be check timing and valve lash. If the valves aren't opening all the way it would be down on power. Outside of this I am at a loss. This bike ran like a top and started up far easier then my newer Honda and just out of the blue started this issue after sitting for about a month. 

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In that last post it sounds like it's better in higher gears now, but earlier it sounded the other way around... better in low gear. Has it changed ?

And.. you have changed the spark plug now ? You mentioned you were planning to.

It doesn't sound like the plug because plugs mostly play up with high compression and engine load, which is highest at mid or lower revs, and higher gears rather than lower. . The blackness on the plug seems to mean it's getting plenty of fuel, perhaps just not firing every time and so burning heaps when it does..  If the motor was flooding for some reason, like the carbies float chamber vent/hose being blocked, it would sort of burble and stumble/surge and not rev,  but not really rev cut. Have you driven a flooding  motor before ? They run and sound different to one starving or missing from spark issues. If it's a diaphragm type carby, have you checked the diaphragm on the slide, and also the needle in the slide, I've seen the needles not have their clip on them for some reason or another and the needle could jump up and down in the slide.. and they ran erratic and rich.

And you say a rev limiter.. rev limiters cut the ignition momentarily right, so the engine goes from full power to cut, then abruptly back to full power.. and the bike jerks and bucks.   That is what it's doing right.. It's how I read your description.. as opposed to getting to high revs and then fading the power away .. If it's fading the power away/going flat, that's a whole different thing.. Maybe flooding.

If it's the rev cut sort, the voltage regulators can cause that on some bikes. They are meant to get to a certain voltage and then reduce the voltage by shorting a certain amount of it out through a resistor to ground, but still let a bit of power through to keep the voltage about thirteen volts. If there's no battery or a bad wire the regulator sends some power to earth, then detects that that hasn't lowered the voltage enough and so shorts it fully to ground, killing everything momentarily till the revs and volts drop again. Sometimes putting the headlight on will let you get a few more revs out of them, which gives a clue or confirmation..

The sitting for a month and then having the problem sounds sort of like a clue perhaps, but we don't get freezing conditions here. Perhaps someone knows of something that happens when things freeze.. like fuel or electrical things that go bad.

Hope that gives you a few more ideas to consider..

 

 

Edited by Mech

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It's either a bit of water in the fuel or a blockage in the carb.  I would throw that Peak CDI in the yard as far as I could though and try an OEM CDI if I had one before doing too much more investigation. 

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So running it around the yard when I say it seems to hit a rev limit it seems to get a quick rapid stutter in the rpm. It doesn't seem as snappy as it uses to be but it does rev up. Once I get to 3rd gear it has no power. It appears if you hold it half throttle it will maintain but if you push it further you can feel a slight drop in speed and the engine is boggy. I'm not sure I would say it is flooding as it doesn't seem to get worse and as soon as you back off it seems ok. If you hold it wide open to long it will just quit like you cut ignition. The bike in 3rd gear and up can't reach high rpm and reacts like you need to down shift as it is over loaded, which makes sense give it can't be rev'd up. 

I have been reading through other forms and the manual which lead me to testing the voltage regulator. I had tested to see if it was charging before but idle or low speed. The results I found where as follows 

engine off batt voltage 12.6 volts 

engine idle lights off 13.3 

engine idle lights on 13.6 

engine rev lights on 12.9 

it seemed odd the voltage dropped as rpm increases. The test spec said it should be 14-15 volts. I then tested the stator for voltage output which they say at 4000 rpm 50-75 volts. I don't have a tach but revving to a point around 4k I am 58-64 volts. When I Ohm the stator with warm engine I am 0.7-0.8 ohms when cold I am 0.6 ( meter only does one decimal place.) and infinity to ground. The spec doesn't specify hot or cold but it following the procedure through charging system it specifies get engine warm to test step one ( batt voltage) and the stator resistance is like step 5 or 6. The listed spec is 0.3 to 0.46. I then tested the regulator on the bench for resistance to spec and it is 32 kohm in one direction and infinite in the other. it is to be infinite in both. I have now ordered a new one to swap it out. I am not sure what to think about the stator as it is reading high resistance but outputting correctly. 

Is there a reason that the aftermarket CDI is hated that much?

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Hi.. No reason to hate aftermarket but the problem sounds electrical. You've tried two cdi so it makes it unlikely to be that, but... If Mark has problems with them perhaps he is onto it..  In my experience cdi either go or not.. But we can all learn.

Regulators and charging though can cause all sort of problems, from really unbelievably heavy loads on the motor, as though they are seizing,  to that rev-cut stuttering..  Have you inspected and checked all the connections and earths for bad or intermittent connection ? Do you have headlights ? Does turning that on and off make a difference as you ride ?

And perhaps there's a wire that rubs when the vibrations happen from the engine or engine flexing on it's mounts ?

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The aftermarket for CDIs are pretty much all the same Chinese junk with a failure rate around 90%. Rick's are the only CDIs I have seen that aren't failure prone. To the OP though, great work on diagnosing the stator. From your numbers I'm leaning towards stator or more likely regulator/rectifier going on the fritz. Electric is hard to diagnose because it can behave differently in testing and under load. Sometimes under load they act funny. Had a spark issue I traced once for an eternity and it turned out to be the plug. It would not fire under compression but would in open air. Sometimes they are just strange. 

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4 minutes ago, MarkinAR said:

The aftermarket for CDIs are pretty much all the same Chinese junk with a failure rate around 90%. Rick's are the only CDIs I have seen that aren't failure prone. To the OP though, great work on diagnosing the stator. From your numbers I'm leaning towards stator or more likely regulator/rectifier going on the fritz. Electric is hard to diagnose because it can behave differently in testing and under load. Sometimes under load they act funny. Had a spark issue I traced once for an eternity and it turned out to be the plug. It would not fire under compression but would in open air. Sometimes they are just strange. 

Thank you and as for the CDI I tried to go with a Ricks but they seem to be out of stock up here in Canada for them so I went with what I could find. I tried a cheap amazon one as it was next day delivery and like you said cheap china parts... didn't work out of the box. Put this one on from Kimpex and ran like a top again. I had heard some bad reviews of them not working out of the box but when I heard it fire I forgot all about it. If this ends up continuing I will search for a Ricks again. h

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"It would not fire under compression but would in open air. ".. That's a known phenomenon. There's more resistance in compressed air than air at sea level.. And it makes quite a bit of difference too.. Have you seen one of those old sparkplug testers where you put the plug in, push a button and it starts to spark, you can see through a glass window, then you turn on a tap and let compressed air in and the spark falters, and at quite low pressure too sometimes.  It can be tricky alright and I've wasted time before trying everything else. Stale fuel causes almost the same problem if it gets on the sparkplug..

 

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So I have installed a new regulator and the charging is now 13.6 idle and 13.9 reved up. The engine still falls flat when given throttle and now appears to be doing it in first and second gear as well. These bikes have a very low first gear and it bogs right out trying to get off the drive way. I will post a video shortly. 

 

 

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Posted (edited)

It sounds to me as though the throttle really isn't opening. Check the  carb to see if the slide is actually  moving  with the throttle . and the needle is moving with the slide.

 

Edited by davefrombc

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Yeah check the slide needle is being held in the slide. I've seen them loose and jumping up and down.

And this thing, it's not temperature related is it ? It doesn't seem to fail after it's warmed up more than at first start and few minutes ?

And do you have a timing light ? Can you check the ignition timing and advance ?

Does turning the headlights on make any difference to the running/problem ?

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I will have to see if the slide is moving and if the needle is floating around. They are a very odd carb with the throttle running a butterfly and vacuum running the slide. the slide seems to move freely when I have it apart. 

 

When you open the throttle part way it seems ok but the more you open it the more flat sounding it gets and the rpm doesnt increase.

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So I have gone over everything and while waiting on a call back for the CDI I checked the valve lash which was out. set it correct and it is like a new bike again. 

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Ha good one.. getting hot and tightening up..  I've seen it before on things, but normally with a whole lot of spitting out the carby.. 

In all the manuals for auto stuff the first thing they always say we should do is, do a standard tune and servic and check everything is to spec...  Boring !!  Haha.

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