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Motorcycle Discussions => Japanese Bikes => Topic started by: petrolderek on May 14, 2018, 11:30:57 AM

Title: yamaha ds5 engine
Post by: petrolderek on May 14, 2018, 11:30:57 AM
Hello
I am new to this forum. I bought a yds6 which has the earlier ds5 engine fitted. It is a usa import and was piston seized, I have fitted new rings and cleaned the carbs. It starts first kick but is not running as it should its well down on power. The left cylinder is not firing as it should there is very little smoke from the exhaust and the head is only warm to touch after running for a few mins while the right is hot.
The spark is good I have switched the plugs around and removed the carbs which seem ok. I am thinking the crank seals are leaking. The question is can the seals be changed with the engine in, what is the best way of checking them first.
Title: Re: yamaha ds5 engine
Post by: murdo on May 15, 2018, 10:07:19 AM
The left cylinder crank seal keeps the gearbox oil out of the crankcase so I don't think it would be leaking, otherwise you would have clouds of smoke.
Look to the setting of the ignition points and timing under the right side engine cover. The plates move seperately for each cylinder and is easy to get one wrong.
Title: Re: yamaha ds5 engine
Post by: petrolderek on May 15, 2018, 02:25:55 PM
Thanks I will check that.
did a compression test and its down to 75psi on the left and 90psi on the right. sounds like the new rings haven't bedded in. Might have to rebore it.
Title: Re: yamaha ds5 engine
Post by: Rex on May 15, 2018, 02:40:13 PM
Did you glaze-bust the bores before reringing it?
Title: Re: yamaha ds5 engine
Post by: petrolderek on May 15, 2018, 04:51:42 PM
no I just used a bit of fine wet and dry by hand.
Interestingly I had the carbs off to check them when I couldn't find anything wrong I put them back on and tried to start it without fitting the oil tank back but it wouldn't start without it on it was as though there wasn't enough compression  without the oil lines connected. When I connected the oil line it started but its still not firing on the left side. I checked the timing and the left side was retarded so I have set it the same as the right side but its the same. Connected my neon strobe and its sparking all the time but its not firing the exhaust is cold. I think its time for the barrels to come off.
There is a pointer at the bottom of the points case I take it this is to set the timing. The points to open just as the marks align is this correct. How do I know the pointer is in the correct position it seems to be adjustable.
Title: Re: yamaha ds5 engine
Post by: petrolderek on May 15, 2018, 09:57:24 PM
Seems like I dropped a clanger. Have taken the barrels off took the rings off and put them in the bore there is a .040 in gap in the rings. I have either measured the bore wrong or ordered the wrong rings and not gapped them. No wonder it didn't have any power. I thought the bore was standard I will have to measure it again and get some correct rings. I have set the timing at 1.8mm btdc is this correct I cant find any info on this engine.
Title: Re: yamaha ds5 engine
Post by: murdo on May 15, 2018, 10:23:40 PM
From memory (I sold my YDS5 about 4 years ago) 1.8 to 2mm is correct.
Title: Re: yamaha ds5 engine
Post by: iansoady on May 16, 2018, 12:30:20 PM
Aren't they pegged? Ring gaps on 2 strokes can be misleading.