Author Topic: yamaha ds5 engine  (Read 1578 times)

Offline petrolderek

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yamaha ds5 engine
« 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.

Offline murdo

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Re: yamaha ds5 engine
« Reply #1 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.

Offline petrolderek

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Re: yamaha ds5 engine
« Reply #2 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.

Offline Rex

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Re: yamaha ds5 engine
« Reply #3 on: May 15, 2018, 02:40:13 PM »
Did you glaze-bust the bores before reringing it?

Offline petrolderek

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Re: yamaha ds5 engine
« Reply #4 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.

Offline petrolderek

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Re: yamaha ds5 engine
« Reply #5 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.

Offline murdo

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Re: yamaha ds5 engine
« Reply #6 on: May 15, 2018, 10:23:40 PM »
From memory (I sold my YDS5 about 4 years ago) 1.8 to 2mm is correct.

Online iansoady

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Re: yamaha ds5 engine
« Reply #7 on: May 16, 2018, 12:30:20 PM »
Aren't they pegged? Ring gaps on 2 strokes can be misleading.
Ian
1952 Norton ES2
1982 Moto Guzzi V50

Offline petrolderek

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Re: yamaha ds5 engine
« Reply #8 on: May 26, 2018, 01:40:19 PM »
The ds5 is sorted. Looks like when I fitted new rings I only fitted one ring to replace the one I broke trying to un seize the rings from the piston. One ring was ok the other three had way too much gap so the three with too much gap were the originals . I cant believe that the originals were that worn because the bore isn't worn and its standard so the rings that were in must have been the wrong ones. That's possibly why the bike had been left unused for such a long time it wouldn't start or it had no power. Its not the first time I have bought one of these bikes from the USA that look in really good condition but haven't been used for years and according to the seller probably (only seized through standing) to find that there is a reason why they were left standing because they couldn't fix them. So be aware when you buy one of these you will need to check everything its not enough to just un seize them and clean the carbs out you will need to find the original reason why they were laid up.
 It runs great now and starts if you look at it. Happy days.

Offline Rex

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Re: yamaha ds5 engine
« Reply #9 on: May 26, 2018, 07:09:09 PM »
Good news, but you surely didn't really think that those bikes (or any other) are just parked and left in running order? We've all seen the "Viet-Nam conscript who never came home" but the reality is more mundane. A minor fault stopped it being used and it was left for "another day" which never came...

Offline petrolderek

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Re: yamaha ds5 engine
« Reply #10 on: May 28, 2018, 12:45:49 AM »
If I am honest I don't mind whats wrong with them but not everyone has the ability to sort them out. I bought a really rough Honda CA77 dream ex USA again but it was cheap. Found it was seized as usual but this one was SEIZED SOLID. I have never had an engine piston seized as bad as this one. Took the heads off but the barrels would not budge. Any amount of heat, oil, coaxing, bashing made no difference There was no evidence of rust or corrosion and only one piston was tight. After two or three days it was time for it to relent so I drilled the piston from the top and drilled out the con rod the split the piston down from the inside it was only when it was completely split right down did it move and even then it was still very tight. The was no rust or signs or damage other that what I had done to get it out.
I happened on some barrels and pistons and put it all back together when it came to the ignition timing it was so far out its a miracle it ever run at all it must have overheated to the point of distorting the piston.

Offline Rex

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Re: yamaha ds5 engine
« Reply #11 on: May 28, 2018, 10:31:05 AM »
I was luckier with the "seized solid mate" CB450 import I bought three years back. The kickstart wouldn't budge in the slightest, but putting it in gear showed the engine was free enough. Took the k/s off and removed the primary case to see the k/s spring was broken, so someone obviously had taken off the case  then replaced it all with the (non-returning) k/s shaft at the bottom of it's swing.
New spring, k/s in the correct position and she ran like a good 'un.

Still a deeply unsatisfying and typically mundane Jap motorcycle though and soon moved on.

Offline john.k

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Re: yamaha ds5 engine
« Reply #12 on: May 29, 2018, 03:12:48 AM »
I swapped two Kawa 400 twins for a drum of hydraulic oil.......both only around 5000 miles,one owner.......one kept inside and polished as an ornament.....the other kept downstairs in the shed where children had been playing with it.......the little dears had filled the tank with "petrol"......from a garden hose.....and water had gradually flooded the whole motor.....that was a mess....And the guy had the hide to complain that the oil was used oil.....Although I was impressed by some of the mechanicals.....the alternator was a stationary field coil/brushless type,generally used only on big truck alternators that cost thousands.      And the motor was quite well made.......No ,I still hate jappas.




Offline petrolderek

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Re: yamaha ds5 engine
« Reply #13 on: May 29, 2018, 07:48:48 PM »
I bought the ysd6 on ebay and when I went to collect it there was a really nice Suzuki GT250 as well so I brought them both home. I cleaned the carbs on the Suzuki cleaned the points lashed a battery on and it started first kick. This bike hadn't run for donkey's years I was amazed that's when it all went wrong. The daft vacuum fuel tap didn't work so I took it off and fitted a normal  one. The bike always started first kick but had a tendency to drip fuel from the left hand exhaust I made enquiries and was told by more than one that they all do this give it a good run it will clear. I went into the shed just after Christmas just to start the bikes and give them a run switch the Suzuki on kicked it it fired and immediately seized solid. I was mystified it didn't even start. Stripped it down and found it had bent a rod. I had left the fuel on it had flooded the engine with neat petrol and hydraulic locked and fired. The problem was the carbs had no overflow pipes on so if the float valve stuck it didn't leak on to the floor it just filled the engine with petrol and there was no drain plugs under the crank case. I rebuilt the engine, fitted some carbs with overflows and we parted company. Best Jap bike I have owned Honda cb500/4 most disappointing Yamaha dt125 would go rusty while you were looking at it and wouldn't pull me out of bed. I have a 65 Honda 305 dream which is brill.

Offline john.k

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Re: yamaha ds5 engine
« Reply #14 on: May 30, 2018, 01:15:25 PM »
Up to around five years ago,everyone had a story of a 1970s jappa with a years use kept in a bedroom or study....and they got it given to them.Now jappas are worth serious money,and no one is giving them away......Cept my nephew gave me the DT175 he bought new......what a wreck.....he sure knows how to destroy vehicles......his new Yammy is driven straight into the back of his new pickup,no ramps,just crash bash.......everything comes easy to the young now,no thought of fixing anything.....just buy new.