HONDA VF750F

Classic Motorcycle Mechanics - - CONTENTS -

Jim Lind­say fin­ishes his V4 project. Test next!

The fi­nal in­stal­ment starts with a con­fes­sion. When I said this was a 700, I had failed to spot the clearly marked 748 cu­bic cm on the rear cylin­der bank. It says VF700 on the chas­sis plate, it says 700cc in the V5 but some­body has slipped a 750 engine in at some point. Whoopee, I’ve got a bit more ca­pac­ity and power than I thought. Boo, I’m go­ing to have to change the reg­is­tra­tion doc­u­ment at some point. The bike was first reg­is­tered in the UK in 1995. The speedo sug­gests that it was orig­i­nally sold in the USA. I’ll do the pa­per­work later. A lit­tle more press­ing was the oil leak from the front camshaft cover, and my de­sire to see what the cams were made of. As you prob­a­bly know, fast wear­ing camshafts were re­spon­si­ble for the early demise of the VF. Some were made of re­ally soft choco­late and oth­ers were crafted from a more in­dus­trial, long last­ing en­gi­neer­ing grade choco­late. I needed to know which of these mine had. The seat, side-panel and tank all have to come off to get to the rear bank of cylin­ders: easy enough. The fuel feeds from the tank to a pump un­der the seat and then back up to the car­bu­ret­tors. I sealed the tank out­let and the feed pipe to the pump be­fore car­ry­ing on. The VF has two ra­di­a­tors. The lower one is of­ten mis­taken by the un­know­ing for an oil cooler. The top ra­di­a­tor, com­plete with its twin fans, has to come off so you can get to the front cam cover: easy enough. Pop­ping out the drain plug re­leased a stream of rusty wa­ter – no coolant here. With the sec­ond drain bung in the front cylin­der bank out, I wheeled the bike into the lane and flushed the sys­tem through be­fore pulling the top rad. The VF has four valves per cylin­der op­er­ated by forked rockers, giv­ing one cam lobe per pair of valves. To get the nec­es­sary clear­ance for the rockers, the camshaft bear­ing caps are a com­pro­mise. They do not fully en­close the camshaft jour­nals, which some peo­ple claim con­trib­uted to the camshaft woes. I am not sure about that, but one set of skinned knuck­les later, I had fid­dled the rear cover out from be­tween the top frame rails and saw that my cams had been made from the en­gi­neer­ing-grade choco­late. Get­ting the leak­ing front cover off was far eas­ier.

Sounds like our Jim has more cubes than he thought he had. That’s good, right?

Those cams too were okay. Phew! The top-end of the engine had sounded okay but I was pleased to see it con­firmed. The rub­ber seals on the cov­ers were both shot; flat­tened and age hard­ened. It’s sur­pris­ing that there was only one small leak. I had an­tic­i­pated the dead seals and bought some new ones from David Sil­ver Spares in ad­vance. The al­ter­na­tor cover had to come off to re­veal the tim­ing marks so I could check the valve clear­ances. The VF runs 0.127mm (0.005in) for in­let and ex­haust, and all were spot on. There was an al­most new air-fil­ter in the air-box, so I put ev­ery­thing back to­gether. I put new spark plugs in. The earth elec­trodes of the ex­ist­ing ones were show­ing signs of ero­sion. A few blobs of grease helped hold the new cam-cover seals in place, but even then it took sev­eral at­tempts to get the cov­ers on with the rub­bers seat­ing prop­erly. I used some non-set­ting Blue Hy­lo­mar gas­ket ce­ment on the al­ter­na­tor cover gas­ket and reused it (Rolls-royce uses Hy­lo­mar, you know, but the as­so­ci­a­tion with blue-blooded priv­i­lege didn’t put me off – some­times you just have to suck it up). The Honda has air-as­sisted forks and an air-sprung rear unit. The forks take a max­i­mum of 6psi and the rear unit a max­i­mum of 45psi. I used the track pump re­served for my bi­cy­cle to put the max­i­mum amounts in. It’s not an op­er­a­tion you want to use a com­pres­sor for. The end re­sult would be messy. With proper coolant in, tank pan­els and seat back on, I took it for another slow spin down the lane at the back of where I live. The lane has the ben­e­fit of be­ing pri­vate but the dis­ad­van­tage of be­ing bumpy and short. Fif­teen miles an hour is about your lot, but it was just enough to tell that the bike was ready for its MOT at my lo­cal place Bikes and Trikes of Peter­bor­ough.

They are used to me turn­ing up with var­i­ous old bikes to be tested. “Hope you’ve got some spare camshafts for that,” the owner shouted across the work­shop as I wheeled it in to the test­ing bay. “Ha, ha Jay,” I said. “You’re the fun­ni­est man at that bench.” I take my bikes there be­cause they are a de­cent bunch of proper bik­ers, they do a rea­son­able line in ban­ter, and be­cause they are thor­ough. I work on bikes a fair bit but I do make mis­takes. I was glad of his at­ten­tion to de­tail when tester Kev spot­ted slack top yoke bolts and the rear brake pipe’s un­healthy close­ness to the rear tyre. He didn’t make me take it away as a fail­ure, but sorted it on the spot. Thanks Kev. It is said that in my town (and it prob­a­bly ap­plies to any town of sim­i­lar size or big­ger) that you can buy an MOT for sixty quid and they don’t even look at the ve­hi­cle. But why would you? I de­cided to take a slightly longer route home so I could get out of third gear. It was a short ride. Any at­tempt to open the throt­tle wide re­sulted in the bike drop­ping on to three cylin­ders with a melo­di­ous ac­com­pa­ni­ment of back­fires. Ah sod it! Back in the work­shop, I looked for sparks on all four pots. That checked out so it had to be one or more of the carbs, I hoped. And in­deed it was. I was ex­pect­ing a blocked main jet, but when I took the float bowl off the front right-hand carb (the sec­ond one I looked at), the main jet was rat­tling around loose. It had be­come un­screwed from its emul­sion tube. The carbs looked like they’d been apart for clean­ing and some­body The main jet should be screwed into its emul­sion tube. It wasn’t, so once off the pi­lot jets the bike only ran on three cylin­ders. Rather than trust to luck, Jim checked the other carbs as well. had for­got­ten to tighten the jet. To be on the safe side, I checked the re­main­ing two in­stru­ments. I re­fit­ted the car­bu­ret­tors, a bit of a chore on a V4 but not too bad. On start-up, my labours were re­warded by petrol run­ning hap­pily onto the hot engine from the front right-hand carb. Gaah! I though the float bowl seal had looked a bit past its best but had hoped to get away with it. Fid­dling a stubby screw­driver un­der the carb to nip the screws down did as much good as I thought it would – none at all. The seals are only avail­able as part of a re­build kit and cost 40 quid per car­bu­ret­tor. Blue Hy­lo­mar, as well as be­ing the non­set­ting gas­ket ce­ment of the aris­toc­racy, is also fuel re­sis­tant so I tried that first: carbs off, carbs back on and this time the petrol stayed where it should. Bliss! Out on the road again (taxed by now) and this time it pulled like a V4 train on all cylin­ders. I was dead pleased with the re­sult of the re­furb. It red­lined through the first three gears, cracked a ton, stopped com­pe­tently and caused a cheesy grin to break out on my face. What was even more sur­pris­ing is that it han­dled pretty well for a 32-year-old mo­tor­cy­cle. Over the next few days I put a hun­dred miles on the bike and with each mile my ap­pre­ci­a­tion of it grew. The Bridge­stone BT45 tyres are pro­vid­ing more than enough grip to tempt me into silli­ness. I also hap­pen to love V4 en­gines al­most as much as V-twins. Un­til I’ve fin­ished re­build­ing the blown engine on my KTM RC8 R, the VF is go­ing to be my daily trans­port. I don’t think I’ll be com­plain­ing about that too much, and I’ve still got a com­plete bike in bits that will form the ba­sis of another project in the fu­ture. So what’s next? Well, I’ve got to get the KTM fin­ished. Af­ter that, there is a dropped Tri­umph 955 Day­tona to pick up and I have a 1985 Yamaha FZ750 tucked away in one of the lock-ups; de­ci­sions, de­ci­sions.

WORDS AND PHO­TOS: JIM LIND­SAY

Not bad for a quick re­furb and an ex­cel­lent hack while Lind­say is re­pair­ing his un­re­li­able mod­ern ma­chine. Old V4 still looks pretty good to­day.

Oil was drib­bling from the front cylin­der cover. Hon­das don’t leak oil, do they?

The al­ter­na­tor cover has to come off to re­veal the align­ment marks for ad­just­ing the valve clear­ances.

The age-hard­ened rub­ber seal was the cause of the leak from the front bank of cylin­ders. The rear one was not much bet­ter.

Top ra­di­a­tor had to come off to get ac­cess to the front cylin­der head cover. It was flushed be­fore re­fit­ting.

The cams on Lind­say’s bike turned out to be good, not choco­late! Valve clear­ances were spot on.

Rusty wa­ter was all that filled the cool­ing sys­tem.

Plas­tic bag, ca­ble tie and cap head bolt keep muck out of the fuel.

Jim runs the fin­ished VF up the lane at the back of his house to check all is okay be­fore it goes for an MOT.

This is where you add air to the rear sus­pen­sion unit to a max­i­mum of 45psi.

Main jet. Emul­sion tube.

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