Inside the belly of the beast
1985 Yamaha RD350 YPVS
It’s junior Tyler’s first ever big bike stripdown – with Gary and Al on hand for ‘friendly’ advice
In the last gripping instalment of Project Powervalve, we discovered that some amount of chaos had been wrought by rodents in the airbox. This resulted in something that looked like granola in the bottom of the airbox, carbs and reed blocks and as far as we could guess, even beyond that. Lifting the barrels revealed a rebore and new pistons were in order and there was no question that the engine would have to come down to get the crank out as one of the big-ends was graunchy.
Tyler was keen to remove the engine from the frame himself then strip it down with minimal intervention. Gary and Al were more than happy to stand around drinking tea and coffee while offering the odd bit of advice of varying usefulness. It was Tyler’s first-ever engine strip. “Get stuck in,” said an encouraging G, “but don’t be afraid to ask for a hand if you need it.”
With the gearbox plug out to let the oil drain – we’d got rid of the coolant last month when we lifted the barrels – first off was the sprocket cover, revealing yet more mouse muesli nestling
at the bottom of the casting. Tyler got the spring link off with pliers, miraculously leaving everyone’ s eyesight in taccr at, nak np din th–as tc ra an pd.o th net he anci en tu nlub ed chain w er eric gohnts,tighneef dr et sohtshteu ff scrap pile.
Off with the oil pump cover and out with the cable then Tyler withdrew the pump itself. Out with the engine mounting bolts and the tie-rod bolts under the engine, a quick check round in case any fasteners or electrical connectors had been missed and Tyler called on Al to help lift the engine out of the frame.
With the motor on the bench the time for truth as to exactly what might be required, and more importantly what it all might cost, drew closer. At the start of operations, Tyler had been adamant that he would be using only genuine parts throughout the rebuild. This had caused some raised eyebrows with Gary and Al, who are rather tighter of wallet. As the strip progressed, Tyler’s resolve in this area started to shift slightly.
“There are some areas where original equipment is definitely the way to go,” said Gary between mouthfuls of Maxwell House (milk, one sugar), “head gaskets certainly, other gaskets preferably, crank seals probably, although these days there is some good aftermarket stuff out there and reputable two-stroke specialists won’t sell you rubbish, even if you insist on it.” Alan was of a similar opinion: “I always use OE head gaskets but happily use aftermarket stuff for the other gaskets and seals if available.”
Tyler cracked on with the strip as he contemplated his options. Soon the clutch cover was off after a judicious blow or two from the hide hammer. Gary requested a penny, not for anyone’s thoughts or to send after all that instant coffee but rather to lock the primary gears with while the clutch was undone. With the pressure plate and friction and steel plates removed then the clutch tab washer chiselled back, Tyler deployed the air wrench on the nut and the one for the primary gears too. “Didn’t need a clutch holding tool then,” he mused. Although he might have found one useful in the absence of a compressor.
Off with the generator cover and the flywheel’s nut, again made easy by the impact wrench, and it was a convention defying ‘lefty tighty and righty loosey’ moment for Tyler using the left-hand thread flywheel extractor tool, the satisfaction of which never grows tiresome.
TYLER HAD BEEN ADAMANT HE’D BE USING ONLY GENUINE PARTS. THIS CAUSED RAISED EYEBROWS WITH TIGHTWADS GARY AND AL. AS THE STRIP PROGRESSED TYLER’S RESOLVE IN THIS AREA STARTED TO SHIFT
With the flywheel off and stator and pickups removed, Tyler was getting close to splitting the cases. First the screwed in bearing retainer under the clutch basket had to be removed – it bridges both of the horizontally split cases, Tyler borrowed one of Pete O’dell’s T-bar JIS screwdrivers to ensure safe removal.
Next Tyler cracked off all the crankcase bolts top and bottom. “Yamaha are very good at hiding those under some unexpected places,” said Gary, prompting Tyler to check then check again before spinning out all of the bolts. “Where shall I hit the cases to get them apart?” asked Tyler, waving the mallet dangerously close to a thin part of the top case. “Not there,” yelled G before guiding Tyler to the more substantial areas of the castings. Tyler was less keen to smack his own cases hard than Gary was, so offering him the hammer, G revealed the gasket line with one well-placed tap.
That meant Tyler could at last lift the cases to reveal just how much work would need to be done. We’d already established the need for a crank rebuild, a view only compounded by more mouse mayhem in the bottom of the left side of the case under the flywheels when the crank was lifted out. The crank seals were more like bakelite than rubber too. Gary spun the mains to demonstrate just how shot they were. Even against the background noise in The Motorcycle Works workshop (never anything less than a buzzing hive of ceaseless activity) you could hear them grumbling, a little like Gary when asked to MOT a knackered Chinese 125.
There was plenty of good news as far as the gearbox went. Even the selector forks were in far better condition than you’d expect to find them on a hooligan favourite like the 350 YPVS.
So a crank and top-end rebuild should be the biggest of Tyler’s issues getting the bike back on the road. Not at all bad for a bike that was a totally unknown quantity until its inaugural stripdown at the hands of Tyler.
“I just can’t wait to ride it,” said the protege as he headed off with his spare parts shopping list.
THANKS TO The Motorcycle Works 01733 578883, themotorcycleworks.co.uk
“WHERE SHALL I HIT THE CASES TO GET THEM APART?” ASKED TYLER, WAVING THE MALLET DANGEROUSLY CLOSE TO A THIN PART OF THE TOP CASE. “NOT THERE,” YELLED G GUIDING TYLER
It’s a big moment for the wee fella
Just as well it came out – all knackered save the gearbox
A beaming face where once there was a tired engine
Where it all starts to get a bit more serious
All his own work – top effort Tyler. So far so good