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rusjack
08-22-2009, 3:22 PM
Bike details
-new gasket set for the top end
-new spark plug
-fresh oil
-fresh gas
-new battery

ive been working on this one for awhile.

engine has no kick, so electric start only. when i hit the electric start, engine turns over, and chugs.
has spark, tried widening the gap for a hotter spark as well.

pretty much, nothing will combust in the engine. I have compression, lots of spark (i have tried several different gaps), i have re checked the valve timing, valves are seated properly (no solvent can escape thorugh valve seats when poured into the intake and exhaust ports)

im at a stand still with this bike... for something so simple, im missing something. ive tried different coils and i yeild the same result.

anyone have any idea that will get me thumping?


edit: I forgot to mention this happens as i try to put gas down the spark plug hole to use as starting fuel. i get absolutley no combustion in this engine. i cant set the spark timing, the SR uses that TCI unit to spark when it's supposed too.

eightthirtysixcc
08-22-2009, 7:19 PM
Static time it and make sure the timing is correct. does it have a mechanical advancing unit or is it built into the cdi?

Don’t just pour fuel down the plug, cup your hand over the back of the carb until you feel gas on your palm then give it wide open throttle as you hold the starter. It may take quite a few turns to get the mixture right.

if valve timing is good, ignition timing is good, it has spark, and it has gas and still don’t start? Do a compression check or leak down.

Make sure that bitch don’t have bad ring/ valve seat. It's a single, this should be easy.

boogieman
08-24-2009, 9:01 AM
First thing I would check is timing. If the points or electronic ignition are wired backwards it won't start, can even backfire out the carbs and burn your bike/garage down. I had mine backward and I fought it for 3 hours till I asked around and figured out what was going on. There has to be a way to set the timing/spark.

Even if you are getting spark, unless it's at the right time, (with proper fuel/oxygen/compression) it won't do a thing.

eightthirtysixcc
08-24-2009, 9:42 AM
You cant adjust the spark on the old ecu's. The question is if it has a mechanical advancing unit or not. If it does and its stuck to full advance you wont be able to start squat.

Just static time the thing, its easy. Take a test light and put the probe on the coil power feed line. Then rotate the crank by hand until you hit the timing mark. If your test light illuminates at the mark it is good. If it is lighting advanced or retarded something is aint right.

Help me, help you and check all this shit and get back.

It is a Yamaha so I wouldn’t be surprised if they had some kind of funky retrofitted ignition unit. The fact that you get spark leads me to believe the ECU is good. They tend to work well, or not at all. If the top end was taken apart some bonehead could have set the cam timing wrong. it could be a tooth off or worse.

rusjack
08-24-2009, 1:26 PM
Cool, thanks for getting back to me with this.

My next step is to get back my compression gauge tonight as test again, and test with the oil in to see if it needs new rings. I have a set here, but when i bought the bike this winter I knew nothing about engines, and the previous owner said the piston didn't need them. Slipped my mind last time I had the top end apart.

When i bought the bike it had a broken rocker arm, so i spent the winter months learning about top end repair, did all the cleaning and checking, and everything seems to be functional and clean now. The valve/cam timing is set right, ive spent a few days learning, re-learning, doing and re-doing that.
The top end has a new gasket set, new o rings everywhere. Ive replaced both rocker arms, checked everything I could, and cleaned everything as much as I could. I checked the valve seals by pouring solvent into the intake / exhaust ports and checked to see if any could leak out the valve seals, and nothing could. no carbon left on the valves, either.

The ignition unit is one of the TCI units yamaha uses, I do not believe you can set the ignition timing at all with this. its a box with a PCB inside of it (http://www.jetav8r.com/Vision/TCIRebuild/TCI_Rebuild.html) I dont own a timing light, but in the repair manual it says "if timing is incorrect, replace part" and those TCI units cost a pretty penny.



Instead of using a timing light can i just rig up a 12v light to ground and a probe on the hot to the coil?

eightthirtysixcc
08-24-2009, 2:04 PM
Errrr...

"Just static time the thing, its easy. Take a test light and put the probe on the coil power feed line. Then rotate the crank by hand until you hit the timing mark. If your test light illuminates at the mark it is good. If it is lighting advanced or retarded something is aint right."

Test light = 12v light = ground and a probe

rusjack
08-24-2009, 2:09 PM
too many people telling me I need a timing light from a store in real life + groggy morning. Thanks.

eightthirtysixcc
08-24-2009, 2:17 PM
The only thing a timing light does is make it easier to do adjustments on the fly while the engine is running. Since you cant make adjustments, there is no reason to have one.

P.S. when you rotate the crank if the timing marks are on the right side of engine spin the crank clock wise. If the timing marks are on the left side spin the crank counter clock wise. It does make a difference. also do it with the spark plug out so you don’t have compression fucking with you.

rusjack
08-24-2009, 2:56 PM
edit : manual answered a dumb question

rusjack
08-24-2009, 3:25 PM
So i cant get anything with a light hooked up.

Grounded on one lead, other lead to the spark plug lead wire. It should flash in the same way the spark plug should spark, at the time time, yes?

I cant manage to get that to happen. Also, if I just look at the spark (plug grounded) it should do the same thing, spark when the light SHOULD flash. I can only get it to spark when im using the electric start button to move the engine... spining the crank by hand wont make the plug spark, so in that sense, spinning the crank by hand wouldnt make the light come on, correct? or am i missing something...?

eightthirtysixcc
08-24-2009, 3:50 PM
Make sure the key is on when you spin it. Go very slow when you spin. Make sure the bulb in the test probe is not burnt out. Attach the ground lead on the probe to the negative terminal on the battery. The light should come on when the timing mark is lined up with the electronic pick up. Make sure you have a very good connection on the coil with the probe. Sometimes the little point on the end is not good enough.

Maybe you are on the wrong wire?

rusjack
08-24-2009, 4:33 PM
Make sure the key is on when you spin it. Go very slow when you spin. Make sure the bulb in the test probe is not burnt out. Attach the ground lead on the probe to the negative terminal on the battery. The light should come on when the timing mark is lined up with the electronic pick up. Make sure you have a very good connection on the coil with the probe. Sometimes the little point on the end is not good enough.

Maybe you are on the wrong wire?

im using a brad new taillight as my test light. ground lead is on the negative terminal, and positive lead is right on terminal in the coil, going as slow as i can I cant find a spot that will light up. ive been doing this for most of my day now...

Could it be the actual TCI ignition unit wont let the current flow unless the powers coming from the electric start? I have a feeling its not me and its just the design of the ignition unit.

rusjack
08-24-2009, 4:47 PM
this is a clip from the manual. I think its saying what im trying to say

eightthirtysixcc
08-24-2009, 4:47 PM
It's a Yamaha I have seen weirder things... But probably not the case.
Try placing the light off the wire coming from the magnetic pick up. Pre-E.C.U.

*****This is very IMPORTANT, how many wires are coming off of your tail light?****

Also don't attatch the wire to the spark plug wire cap. Hook up to the power wire going into the coil. This could be your problem.

Can you get me a scan of the wiring diagram? That may help.
Plan b: get a friend to push you fast down a hill in 3rd-4th and try bump starting it.

eightthirtysixcc
08-24-2009, 4:51 PM
Fucking retarted Yamaha, it looks like you are correct they have some lame fail safe.

It has an electronic timing advance so the odds of something being whacky with the ignition timing is slim.

Compression test at this point. Hook it up and hold the throttle wide open and crank it over until the needle stops moving. Let us know what the reading is.

rusjack
08-24-2009, 5:04 PM
It's a Yamaha I have seen weirder things... But probably not the case.
Try placing the light off the wire coming from the magnetic pick up. Pre-E.C.U.

*****This is very IMPORTANT, how many wires are coming off of your tail light?****

Also don't attatch the wire to the spark plug wire cap. Hook up to the power wire going into the coil. This could be your problem.

Can you get me a scan of the wiring diagram? That may help.
Plan b: get a friend to push you fast down a hill in 3rd-4th and try bump starting it.

two wires, single filament bulb. ive tested and re tested it on just a 12v battery and it works fine. i double check the bulb after every test.

the plug cab ive been using has a 5K resistor in it, and thats enough to not light the bulb when its in series with it, so ive been going straight to the terminal on the coil. you say power wire going INTO the coil? the coil has 3 terminals... 2 lines going in, one line going out to the spark plug. the two lines going in have a constant voltage on them, so the light would constantly be on when touching those. Ive been testing from the terminal that would go to the spark plug


thanks for your constant help by the way!

rusjack
08-24-2009, 5:07 PM
Compression test at this point. Hook it up and hold the throttle wide open and crank it over until the needle stops moving. Let us know what the reading is.

I have to meet my friend at the bar tonight shows borrowing it to give it back to me. I'll have a reading in the afternoon tomorrow, if you know what i mean. Ill do the oil test while i'm at it, and probably end up with new rings in it.

thanks!

rusjack
08-25-2009, 3:56 PM
45psi. what a crock of shit.

Well, I bought this bike to learn on. Seems to be worth the 200 canadian dollars... whats that in US.. 45 bucks?

eightthirtysixcc
08-25-2009, 8:49 PM
Yup you got a stinker there. 40 is very extra low but thank the lord it's a single cylinder single cam engine. Rebuilding the top end wont be hard at all.

Did oil help raise the psi?

rusjack
09-02-2009, 2:48 PM
I tore down before trying with oil. I had new rings and just wanted to get at it

Which i seem to be doing today, took a long break.
Anyway, anyone have some pointers on getting some rings out of this piston? they are jammed right in there and i cant get them free. solvents to loosen it up?

eightthirtysixcc
09-05-2009, 10:20 AM
Find the split in the ring and get a small flat head (the tiny ones) and flare it out. Use a small hammer and tap in if you need to.

When you install the new rings make sure you put them in the correct order. There is a compression ring an oil ring and a scraper ring. Also the rings are directional. One side is square (bottom) one side is domed (top) one the edge. Put the dome side facing up.