OzVMX Forum
Marque Remarks => Suzuki => Topic started by: vlxk on June 15, 2015, 11:12:13 am
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Hi everyone, my RM250C2 is close to completion. I had the cylinder bored 1/2mm and everything is back together except fenders and fork boots.
I got ready to start it yesterday, went back over everything to make sure all the nuts/bolts were tight, oiled the airfilter and got it wedged down in there! Poured a little fuel in (using Motul 710 @ 20:1). Gave her a couple of good kicks and she barked for just a second, then nothing. I kicked and kicked with not even a hint of starting.
Changed to clear fuel line to make sure fuel was flowing, good to go. Removed carb to make sure fuel was getting into the bowl because the clear hose shows fuel going into the carb and filling the fuel line maybe a couple of inches above the inlet and stopping. I thought the fuel would completely fill the fuel line? still no starty.
Pulled the plug, grounded and kicked it, good spark, I can hear it click and see the spark across the electrode. No starty.
Pulled the carb and removed the bowl carefully to not spill any fuel, bowl is full. Kick it multiple times, nothing.
Pull plug, can smell fuel on the plug, test again for spark. Test old plug for spark, same as new one. I can see the spark when cycling through with the kickstarter.
Removed stator cover, the timing mark is centered under the top screw, although the bottom screw is slightly off center.
I am this close () to trying starting fluid to see if it will fire with that.
I have spark, it seems I have fuel, and I have compression, what can the problem be?? The bike ran when I bought it several months ago. It ran even though the crank drive gear nut had backed out to where it just barely touched the inside of the case. The left side crank seal was in crooked, and the float was way off and the pilot jet had been changed to a #25 from #45-#50 as the OE specs say. Now I take the good time and trouble, not to mention expense, to make things right and this is what I get!!! >:(
Anyway, any ideas as to what might be holding things up?
Thanks
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is you rotor siting where it should. it could shear the woodruff key of and that causing your timing being out. hapens to my dads lawnmover all the time. :D
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I had not thought of that. I'll check it out and report back.
Thanks.
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You don't have a bung in the exhaust do you? Seen it plenty of times, guys forget to take it out, bikes won't start, then by the time they realize the bikes are flooded to the point of having to be turned upside down to drain the crankcase. Just a thought.
K
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You don't have a bung in the exhaust do you? Seen it plenty of times, guys forget to take it, bikes won't start, then by the time they realize the bikes are flooded to the point of having to be turned upside down to drain the crankcase. Just a thought.
K
Yep that's a Classic ;D guilty as charged ::)
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Did you remove rag from intake before fitting filter? A mate carted his bike 100 km to a bike shop to find that one. A bit embarrassed!
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and the plug was wet when you removed it? if so its flooded
if it was dry you have a carby/fuel tap issue
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aerostart/start ya bastard problem solved.
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Choke working properly? Mixture screw set currently?
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You guys are great! I travel during the week so I won't be able to do anything with it until Friday night or Saturday.
I don't have a bung plug so that isn't the problem, although I can picture all the hoops one would jump through before realizing the exhaust is stopped up!
I set up the carb per the OE specs, 300 main, 45 pilot, mixture screw 1.5 turns out, float at 13 whatever mm. What about the fuel not completely filling the fuel line between the tank and carb?
Plug was slightly wet, I could smell fuel on it.
There are three marks on the face of the rotor, are those some sort of timing reference?
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Pretty sure that the fuel line not being completely full is normal, I run an inline filter on most of my bikes with black lines & the filters always have a certain amount of air in them
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****Update****
Checked the key under the rotor, all is good there. In a weak moment went down to the local Auto Parts store and bought a can of "Start ya Bastard!" and gave it a try. Believe it or not, it made no difference. Wouldn't even try to fire.
My front yard has a bit of slope so I pushed the old gal (motorcycle, not wife) down the yard and clicked it into 2nd gear...nothing...tried it again and it tried to start. Third time it fired and ran although poorly! Lots of smoke and no rev. I had to really be gentle with the throttle to keep it running.
Since it is a fresh bore and new Wiseco piston I didn't let it run long. A couple hours later I tried it again. I had to push it again but it started much easier that time. Still considerable smoke and spooge was dripping from the muffler/pipe joint. I assume it is/was extremely flooded. I dribbled a bit of 2T oil on the bigend and crank bearings on rebuild.
Third time an hour or so later, it tried to start by kicking but I pushed it to get it going. Here's where the next questions come in. It's running poorly, lots of smoke not as much spooge this time. Just to see what would happen I turned the fuel valve off. After a minute or so the old gal (motorcycle not wife) cleared up and had good rev! I tried it a couple more times with the same result. With the fuel valve open it runs like crap, as it runs out of fuel with the valve closed it cleans up and runs very good. I did a little dance with the valve and kept it going for several minutes.
My first thought is the float level is too high. I was very meticulous with the carb. The float is set at 13.9mm as the manual says. I restored the carb to new specs, 300 main, 45 pilot, (had a 25 in it) , needle clip in middle slot, mix screw is at 1.5 turns out. New oiled air filter. Premium 91 octane no meth fuel with Motul 710 @ 20:1.
Changed the float level to 12mm and it didn't make any difference. With the fuel valve open it runs poorly, close the valve and as it runs out of fuel it runs much better. I did notice air bubbles coming up the fuel line with the fuel valve closed,
What should I look at now? The way the carb was set up when I got it has me wondering. Very low float level, 25 pilot, I don't remember where the needle clip was. Very worn piston/rings. Those settings would make it very lean wouldn't it? I'm about 1000ft above sea level here.
Sorry for the long post :)
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Sounds like the needle and seat are not closing off, there are a few different types off needle/seats for Mikuni's, I alway's put a brand new carby on every resto......30 plus year old carb's are fraught with problems, cheapest part you will buy to make your bike run properly.....under $200 with the correct/extra jets/needles bla bla. Ring T D Hatrick in Townsville tomorrow. ;)
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As above needle and seat.
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Try roll starting it .....with a bit of speed
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got the reed block in
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Has got a crank seal in the RH side? [don't like to ask but clutching at straws]. Only ask that because i think you said it ran ok despite being worn out [etc] & now smokes badly [primary case oil] so that rules out carb unless something outside the square has gone on in the carb. You haven't got a new slide & it's got the guide slot on the wrong side causing a super rich run [cutaway wrong way around]--or--someone's drilled the needle jet [emulsion tube jet--main jet screws into], seen them drilled for alky [methanol] then put back on petrol. No thick washer [any washer] under main jet, although if it has a hat thingy the main jet screws through then it would takes the place of that washer. Sorry, doodling & not thinking hard. Something gone amiss with the choke, like rubber pad gone out of end of it. Something [crumbled old airfilter] got into the air bleed to the emulsion tube. Good Luck.
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Few things I would try:
Try a hotter plug. If it has a 9 in it - try an 8.
Try running it with the fuel cap off? Fiddling with the tap keeps it going you say? Maybe the tank cap is creating a hydraulic lock and not breathing correctly? That doesnt really make full hydraulic sense - but its free to try.
Did you check the reeds? A cracked / chipped reed could cause similar issues?
Try raising the jet needle one clip to lower the needle and lean it off a touch.
Check crankcase breather tube isn't blocked.
Check earth is super clean at coil. Bikes can give erratic spark when revved and foul a plug in a nano-second.
Hope those help.... if not get a green one.... ;)
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For an engine to flood is has to have either no spark to burn it but yours fires so its not sparks. This leaves the carb being the problem, only one way for fuel to get in and thats the needle and seat, this also turns the fuel off when its full. if it doesnt.. it floods.
AS mr crocket has said Mikuni do a few different types. make sure the needle you have matches the seat you have.
if its right main seal the gearbox oil usually goes milky.
could pay to pull the tap and check it for crud while you have the spanners out. you may have more than one problem confusing the issue but I would start at the needle and seat
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While you're dealing with the needle & seat drop the float in a container of hot water, if it has a leak it will start fizzing as the air inside it heats up. Have had similar problems with my yz465 & a cracked float on 1 side was the problem
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my thoughts for the day--if it was float valve [needle & seat] related then fuel would be pssing out somewhere [overflow/breather etc]. Not being suzuki orientated i didn't realise it was water cooled but regardless if rh crank seal was stuffed it'd let tranz oil in [smoke] but run lean from too much air--umm--unless gearbox breather was blocked i suppose. don't suppose the piston has windows like yamaha as have seen one back to front causing headaches [lean & gaspy--very gaspy]. We're all waiting with baited breath for the final outcome. thanks.
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Sounds like the needle and seat are not closing off, there are a few different types off needle/seats for Mikuni's, I alway's put a brand new carby on every resto......30 plus year old carb's are fraught with problems, cheapest part you will buy to make your bike run properly.....under $200 with the correct/extra jets/needles bla bla. Ring T D Hatrick in Townsville tomorrow. ;)
As my fellow mechanic said, don't stuff around with 30 yr old carbys, we've been there done that! $200 and another 30 years of use.
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Well I pulled the carb again and checked out the needle valve. I remember when I first went through the carb at rebuild the needle looked good to me. There wasn't even a hint of wear on the tip of the needle. I polished it slightly just because and reinstalled it.
The reeds are perfect. Crank seals are new with the rebuild. Since it cleans up and runs good as the fuel level drops I don't think it is an electrical issue. It does have the hat thingie under the main jet. I will try the hot water test for the floats next weekend, maybe one is heavy? They both seem to float pretty well in the fuel in the bowl.
So today I had a thought, what about pulling the bowl and hooking up the fuel line and do a test to see if I could stop the fuel flow. I can stop the flow using my finger to raise the float lever dealie. I realize even the lightest pressure from my finger is probably more than the floats raising the lever. But now I am not sure about the needle. I guess $20 for a new one would just eliminate the needle as the problem.
Does anyone know what the number on the seat means? Mine has 3.0. I have searched the interweb and there many different options available. Some have 1.5, 2.0, 3.5. I suppose the number is a reference to flow rate but I'm not sure.
I'm off to work tomorrow so I won't have any updated news until next weekend.
Have a great week and I'll check back in a few days.
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That number is the inlet orifice size, the port diameter, that the needle seats against.
The bigger the number the more flow- and the more pressure head trying to push the needle off the seat.