Rookie Yamaha R5 engine rebuild

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Lowered13

Active Member
I have started to rebuild my yamaha R5 engine and took off the top end and the side covers. I took the bolts out to separate the two halfs of the transmission. Not sure what the best way to separate them is. Also what should I replace well I am rebuilding it? I have to replace the crankshaft and the pistons and get it bored and I will also replace the gaskets.
 

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The two Pictures are where I am at in the rebuild (so not far). But any advise on next steps or advise in general would be appreciated.
 

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You need to replace ALL of the seals and gaskets. You can find them at several online shops or on EBAY.

Hit the retainer nut on the clutch basket with an impact gun. It'll spin the whole deal, but it will also loosen the nut.

Make sure you remove all the bolts on top and all nuts on the bottom. When I split my cases (they're glued together) I ran a coupke of the longer case bolts into some of the shorter holes. After bottoming them out I tapped the bolts with a rubber mallet, separating the cases enough to get a wood wedge in there to pry them apart.

When reassembling, make sure to properly lubricate everything. Don't drive seals in dry. Make sure everything is very clean. Use a good quality case sealer to stick the cases back together.

Replace any rusty or damaged fasteners. Torque everything to spec and in the correct order.

If you don't have a manual, get one.
 
You can make a clutch holding tool with an old steel plate with a handle welded or bolted to it.
 
Motion pro makes a clutch holder. I made one out of some vise grips and two pieces of stainless steel flatbar the was bent 90 degrees on the ends. I'll have to take a picture of it and put it up in the homemade tools thread.
 
Sometimes you can wedge a penny in the gears and that can immobilize the clutch. not sure about the R5 though
 
SONICJK said:
Sometimes you can wedge a penny in the gears and that can immobilize the clutch. not sure about the R5 though
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good call
 
SONICJK said:
Sometimes you can wedge a penny in the gears and that can immobilize the clutch. not sure about the R5 though
Click to expand...

Yeah that works, even a rag will do between the clutch gear and the primary, but in the pictures there's no crank in the cases.
 
dcracing said:
Yeah that works, even a rag will do between the clutch gear and the primary, but in the pictures there's no crank in the cases.
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Yeah nice used both, but the rag can e a bitch to get out if the Clutch is on there tight ask me how I know haha.
I prefer the penny trick.

Looks like impact wrench it is then
 
Pfoeehhhhh thats nasty. Sodablasting would be prefferable.
The 'bearings' from the crankshaft look really worn. Do you still have the crankshaft?
I would suggest getting fresh bearings and such.
 
Ya I have the crankshaft and yes all the bearings need to be replaced. Someone had it apart before me and didn't put the crankshaft back in so the crankshaft area is pretty dirty.
 
dcracing said:
Pretty dirty but you can't see if the bearings have been spinning until it's cleaned up some.
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there pinned if they spun you could tell

it got filled with fuel and oil the last time it ran or tried to start and sat for 80 years, thats what old varnish looks like
not a big deal unless it really ate in to the alum. i would get a (ebay) crank,if it falls in to spec replace the rubber and go. but take a good hard look at the ing system rd/r5 coils are junk and the gunk in your case tell me that that bike wasnt getting enuff or any spark. it loaded up that what happens.life is only as hard as you make it. get a used crank and when your money ahead rebuild your old one.
 
You've never seen a 40 year old crank rebuilt at some time with non pin bearings? I have. No pics of the crank and I don't like to assume it's original.
Still unsure how you'd "mic the crank bearing surfaces"
 
There's a specific measurement for all of the bearing surfaces in the crank case. If the motor siezed up or was damaged (we don't know the extent of he engine wear) it could have damaged those surfaces. I was trying to save him a real headache down the road. Sorry for that. Won't happen again.
 
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