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Post by jon on May 21, 2022 8:45:27 GMT 1
OEB - yes that's right. But either way, to change it 2mm from TDC only takes a small amount of turn and gets nowhere near the timing marks. There is 2 pickups on the flywheel, which I assume is 1 for each cylinder. Should I try timing it against the other cylinder? I would like to prove whether I have the correct flywheel - no idea why someone would change it - but I don't know how I can do that. The 2 pickups are not technically designated as 1 for each cylinder. It’s a losey system, so both cylinders fire on each pickup. I don’t think it will help you too much, but are you taking into account dwell? At TDC you can move the flywheel about a bit and the DTI still not discerningly move. I always take the mean of wiggling is clockwise and anti-clockwise to find the true TDC. Jon
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Post by shaunthe2nd on May 21, 2022 16:28:32 GMT 1
Have you had the crank rebuilt? Is the flywheel correctly engaged with the key on the shaft?
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Post by clarkey on May 21, 2022 16:45:40 GMT 1
OK so I did as you suggested Tony. New mark for TDC , then 2mm BTDC . Removed the TDC mark. As before, bike started first kick. When I put the strobe on it, the line was right round near the pick-up on the stator. I give up!! I have had enough of it today, so I will now go max adjustment each way on the stator and ride it both times to see if there is any difference. The last time I rode it, the adjustment was in the middle. Arrrghhhhhh.....
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Post by clarkey on May 21, 2022 16:47:14 GMT 1
OK so I did as you suggested Tony. New mark for TDC , then 2mm BTDC . Removed the TDC mark. As before, bike started first kick. When I put the strobe on it, the line was right round near the pick-up on the stator. I give up!! I have had enough of it today, so I will now go max adjustment each way on the stator and ride it both times to see if there is any difference. The last time I rode it, the adjustment was in the middle. Arrrghhhhhh.....
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Post by tony2stroke on May 21, 2022 17:42:05 GMT 1
I am starting to wonder if the CDI unit is at fault, none of this adds up, the keyway and key are in good condition on the crank aren't they, keyway is engaging in the slot of the flywheel isn't it, I mean your not just putting the flywheel on in different places when taking on and off, and flywheel isn't spinning on the crank shaft is it.
Just checking no obvious mistakes, though I am sure you know how to engage the flywheel on the crank, just making sure.
Can you make 1 more check for me, when you put the flywheel on, at TDC, where is one of the magnets on the flywheel (in relation to the pick up) look for the one closest to the pick up, doesn't matter which one is closest, just want to know how far away (roughly) from the pick up the magnet is, and is the magnet before or after the pick up at this point.
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Post by clarkey on May 21, 2022 17:58:48 GMT 1
Thanks Tony. Yes I checked that the flywheel engaged properly on the crank and doesn't spin. I marked TDC very close to a pick-up . I will take a pic tomorrow and post it - in fact I will double check the TDC again. Its c crazy as it starts first kick no problem at all.
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Post by tony2stroke on May 21, 2022 18:41:18 GMT 1
Thanks Tony. Yes I checked that the flywheel engaged properly on the crank and doesn't spin. I marked TDC very close to a pick-up . I will take a pic tomorrow and post it - in fact I will double check the TDC again. Its c crazy as it starts first kick no problem at all. Take a pic of the flywheel at TDC according to your dial gauge will you, and then one at 2mm BTDC, and another showing where the magnets are in relation to the pick up at both TDC and BTDC, so we can see what you are. Don't just go out on it yet, you could blow it up, and that's costly.
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Post by chrisg on May 21, 2022 19:25:25 GMT 1
Im sure your aware, but if the timing is out,even if it starts qst kick, the engine can run hot and even hole a piston. Starting qst kick is a good sign though. Perseverance is the key.
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Post by clarkey on May 22, 2022 17:29:23 GMT 1
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Post by arrow on May 22, 2022 18:14:44 GMT 1
Yeah you have to have the right interference of the dti on TDC. on this engine/timing spec. this would be at least 2.5mm, and no more than 3mm.
So on 2mm BTDC there would still be 0.5mm~1mm of interference.
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Post by tony2stroke on May 22, 2022 18:26:51 GMT 1
In reality, the strobe will give you the correct reading, the standard scribed mark should line up with the raised edge of the back plate, regardless of you finding TDC with a dial gauge, you can't get any more accurate than using the strobe light, its a very simple instrument, it lights when it fires, and that should line up with the raised edge line.
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Post by clarkey on May 23, 2022 14:54:58 GMT 1
Does anyone know any 2 stroke tuners near Watford Herts, as I have given up. I set the timing as per the manual, find TDC and the back 2mm, and this was perfectly aligned with the flywheel timing mark F . When I put the strobe on it, it didn't line up at all (was just outside the left edge of the raised plate on the stator) , and moving the stator to both extremes of adjustment hardly moved the strobe line at all. The bike still won't rev through the range - just holds back - and I don't want to strip the carbs yet again until I am sure the timing is correct.
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Post by Tobyjugs on May 23, 2022 15:42:57 GMT 1
The mm measurement method is a very accurate way of setting your timing. You do not need to find abolute TDC. Push your DTI into the plug hole and just turn turn your engine a little backwards and forwards until the needle more or less stops moving. It does not have to be dead on TDC as you are measuring movement in mm's When the needle is pushed in and dosent go any further this is roughly TDC. Push and adjust your DTI so that the small pointer in the yellow dial is on 5 and adjust the big needle with the white dial to zero, This must be done at the roughly Top Dead Center part you found earlier.
Now turn your flywheel slowly by hand in a clockwise direction when you are in front of it, looking at it. Now count 2.5 complete revoulutions of the big needle with the white background.
Care fully and slowly turn the fly wheel in a anti clockwise direction until the big pointer on the white dial reaches 0, the yellow dial will either read 3 or possibly 7.
This is the correct position. now line up your stator plate to the mark on your fly wheel. If this is not possible you the marks are not correct on your parts or its the wrong parts.
Using degrees to time these engines is really not necesarry unless you are building a very special engine. With a standard engine you can fluff the linear measurement up a bit and with a standard Yamaha ignition set up it wil still run. If its misfiring when set up as above you need to look further crappy carbs, electrical parts or even dodgy reeds.
A strobe light could be confusing the situation. Also Your DTI has a very long stroke, with the engine in the chassis it will be more fidly to use. Check to make sure the movement of the plunger is not hampered by any chassis or engine parts.
Good luck in finding the problem
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Post by chrisg on May 23, 2022 16:24:59 GMT 1
Does anyone know any 2 stroke tuners near Watford Herts, as I have given up. I set the timing as per the manual, find TDC and the back 2mm, and this was perfectly aligned with the flywheel timing mark F . When I put the strobe on it, it didn't line up at all (was just outside the left edge of the raised plate on the stator) , and moving the stator to both extremes of adjustment hardly moved the strobe line at all. The bike still won't rev through the range - just holds back - and I don't want to strip the carbs yet again until I am sure the timing is correct. Ive only ever lined the F mark up at 2.00mm btdc, as per manual, and my bikes always run fine (timing wise at least). Will your bike start 1st kick when the F datum is lined up?
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Post by clarkey on May 23, 2022 16:27:57 GMT 1
Thanks Toby - so this is what I just did. So do you think I can ignore the strobe and assume the timing is correct? I have stripped the carbs several times, had them ultrasonically cleaned , changed the floats and adjusted them, new jets (standard size same as those I removed), and it still won't rev through the range. The bike is standard except for Allspeeds, which they tell me does not require any change in jetting.
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Post by tony2stroke on May 23, 2022 16:54:09 GMT 1
I wonder if your CDI is at fault, none of this adds up, I don't see how a strobe light can confuse the issue, how can you get that wrong, it lights when the bike fires, which should be at 2mm BTDC, and the flywheel f mark lines up with the raised edge at this point, how can you get that wrong.
I am with you on the don't look for something else until you get timing sorted, but the revving problem could be so many other things, after all the parts are all very old.
regards revving, have you removed the big brass balls from the carbs and cleaned behind, an ultrasonic cleaner doesn't always get that clean unless balls removed.
Maybe you are just getting confused with it all, maybe a local member can come round and confirm or deny your findings.
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Post by clarkey on May 23, 2022 17:49:04 GMT 1
Thanks Tony - yes I have removed and cleaned behind the big brass balls ( and replaced them!). Now I am wondering if my strobe light is faulty. This is the strobe on the one closest ( although they were only slightly different when the stator was set at opposite adjustments) share.icloud.com/photos/069cU-as9HiSGLOVkf5z_HBIQ
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Post by arrow on May 23, 2022 17:52:01 GMT 1
Something is wrong here. The line should be rock steady. Yours is wandering round a lot.
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Post by Tobyjugs on May 23, 2022 17:54:03 GMT 1
When used correctly the strobe light doesn't lie.
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Post by tony2stroke on May 23, 2022 18:08:00 GMT 1
Looking at the vid, you are close there, looks like if you turn back plate clockwise as far as it will go, you will line up, but it is jumping around a bit, you can hear the engine note changing as timing moves, 1st off, shut the garage door so you can see the light better, hold the strobe close to the timing marks and take another little vid please, try and hold the strobe shinning down directly on top of the flywheel and timing marks, hold it about 5 inches away.
Can you also take a couple of pics of the magnets on the flywheel, check they are solid on the flywheel, not quite sure what I can see there, but I keep getting a glint every turn, but only once per rotation, just trying to check everything.
Another thought just sprung to mind, your plug and caps are good are they.
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Post by tony2stroke on May 23, 2022 19:00:13 GMT 1
Another little check, if you don't mind while your there doing the vid, check to see if there is any movement up and down when wiggling the flywheel, just want to check bearings are in good condition, it should wiggle about 1/2 a mm, if its more than that it can alter the timing accuracy.
its a process of elimination.
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Post by clarkey on May 23, 2022 19:14:22 GMT 1
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Post by tony2stroke on May 23, 2022 19:34:52 GMT 1
I did not mean the magnets inside the flywheel sorry, I should have been clearer, I mean the 2 raised magnets on the outside of the flywheel, there are 2 small raised surfaces on the side of the outside of the flywheel, they give the pick up the signal to fire, in other Qs though you said you checked these when I asked were they were at TDC and just after, I think you are getting really confused with all this. but looking at your vid, there is something allowing the timing to move, what that is I can not tell you sorry, it could be so many things, best to get someone to look at it for you before something nasty happens through running it like that, it will work out cheaper in the long run, unless someone can come and help you. I am not being funny, but I don't think you have the skills to sort this on your own, you are missing something that someone with experience would spot I think. Even new parts can be faulty, trust me I know from 1st hand experience.
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Post by clarkey on May 23, 2022 20:08:37 GMT 1
I did not mean the magnets inside the flywheel sorry, I should have been clearer, I mean the 2 raised magnets on the outside of the flywheel, there are 2 small raised surfaces on the side of the outside of the flywheel, they give the pick up the signal to fire, in other Qs though you said you checked these when I asked were they were at TDC and just after, I think you are getting really confused with all this. but looking at your vid, there is something allowing the timing to move, what that is I can not tell you sorry, it could be so many things, best to get someone to look at it for you before something nasty happens through running it like that, it will work out cheaper in the long run, unless someone can come and help you. I am not being funny, but I don't think you have the skills to sort this on your own, you are missing something that someone with experience would spot I think. Even new parts can be faulty, trust me I know from 1st hand experience.
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Post by clarkey on May 23, 2022 20:11:40 GMT 1
Thanks Chris, and yes I am getting pretty confused and losing my patience TBH. Yes I did check the position of the magnets, and with the F line aligned one is right below the pick-up. I really appreciate everyone's help. If anyone knows of a decent 2 stroke tuner in the Watford area I would appreciate it.
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Post by clarkey on Mar 15, 2023 12:04:48 GMT 1
Sorry but I should have updated you all on this. The reason for the poor running was oil seals. Had to wait a while to get the cash together, but had the engine rebuilt end of last year, and it now runs fine - only managed about 50 miles running in before the gritter made an appearance!! I haven't checked the timing using a strobe as I am not going to worry about that. So now Spring seems to have arrived, I will be out running it in.Thanks everyone for all your help.
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Post by chrisg on Mar 15, 2023 20:56:52 GMT 1
At least its sorted, happy days.
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Post by tdrpete on Mar 15, 2023 21:27:43 GMT 1
Always check your rubbers aint wore out could get you in trouble in the long run lol glad you got it sorted now time to enjoy well done.
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