Which bike, which issue?

HL500 Yamaha - building the ultimate TT500

Words and photos by Marc Phillips

I guess if you are into building old cars you might want a Cobra replica, if classic road racing is your game then you might want a Manx replica. But with VMX, well you are a bit spoilt, especially if you hanker after a HL replica, as Geoff Morris Concepts (GMC) can help you start building the bike of your dreams with an HL500 replica kit. Most VMX riders are fairly familiar with long historical articles on the HL500 so I will skip that and just briefly mention the background of the HL - it was a hybrid MXGP machine built in ‘77-‘78. It was based on the then relatively new TT500 Yamaha motor slipped into a fairly readily-available Husqvarna frame. The Hallman/Lindquist designed HL500, with veteran GP rider Bengt Aberg in the saddle, was able to make a last-stand, top ten finish for four-strokes, in a class dominated by two strokes. Subsequently Norton Villiers Triumph (NVT) produced two hundred semi-factory Yamahas and Protec, Hallman Racing also sold frame kits in the USA and the HL500 moved into the realm of ooh ah VMX icons.

So that’s the history lesson and now it is time to build your dream racer. Like a lot of riders I chose to start out with a half-assed attempt at building an HL500 replica out of a standard TT500 and the end result cost a fortune. It was an embarrassing pile and ended up being scrapped as I decided to do it right the second time. For the budding HL500 builder I would say first you need a vision of how you want it to look - in the same way some guys are cool to fit a Chev in their AC Cobra rep, some guys are cool with some pretty weird HL500s. I chose a traditional look of white and red, with decent side cover shape, and as much of the ‘good period shit’ as I could find. My ideal was Gary Benn’s HL500 (former VMX magazine cover bike) so that is what I built…….OW forks and unobtainium former Yamaha team bits notwithstanding.

The focus was to get the job done right rather than to recycle old TT500 parts so I will not bore you and horrify myself with any kind of budget forecast. But needless to say you will be well into six digits and at about twice as much as any sane person would expect by the time you kick her into life (think about the price of a new YZ450). By the way, that brings us on to the second thing you will need, a high credit limit piece of plastic with Visa or Mastercard written on it. How does it go? Frame kit $3000, Fox forks $2000, clutch cable $50, finding a way of hiding the credit card statements from your wife, paramour, girlfriend, partner or concubine…. Priceless.

The fun begins by having a plan, it probably doesn’t do any harm to sit with a piece of paper and mull over what parts you intend to use. Making repeated lists of bike part is very therapeutic and a great way to kill time in meetings and ignore people at smoko. The major issues that you need to decide relate to frame, engine, forks shocks, carb/airbox, pipe and wheels. But spare a thought for the minor stuff such as color, fastenings, controls, tank, side covers and seat.

First things first, lets talk frames. You have basically the option of going original, NVT or Hallman, and this may be desirable if you are building a collectable, or, you can buy from the replica frame maker, with Geoff Morris of GMC being the most likely and probably the smartest choice. Geoff has built a great number of them, has improved the strength in key areas such as the front down tube, offers a range of other bits such as polished swingarm, pipes, airbox and his workmanship is impeccable. So as fast as you can say Paypal my money sped off to Geoff and some time later a box turned up with GMC frame, GMC alloy swingarm, swingarm bearings (which are not cheap), alloy airbox and stainless surgical grade exhaust.

The money moves fast but the bike moves slow, would seem to be the case at first and in my case even at seconds. Now for the motor. Here you can go original TT, with XT and SR as other options. The motors are not exactly rare so I would look for a good engine rather than a basket case. Things to watch out for with the TT and XT mills are flogged out engine mounts, plus trashed casings from previous chain derailments are almost standard. The TT and early XT also limit you to points ignition, some guys love ‘em, but some guys love magnetos as well. I went for early SR motor for the reasons of heavier flywheels and CDI ignition, which allowed me to wire the bike pretty clean and factory looking. It is also worth considering that the SR engines are still in production in Japan so EVERYTHING is available.

Why build a special bike with a stock motor I hear you ask, no good reason is the answer. So how much you bomb your motor and how much you turn it into a beast is up to you and your LV wallet. A good middle of the road tune will see you with 540cc piston at 10:1, go easy on compression, megacycle or WB cam, 38mm Mikuni, ported head and nicely rebuilt bottom end. If you feel the need for 600cc strokers with Carillo rods and bomb proof NEB gear clusters it is all out there and please do not let me discourage you. I admit to having a Daytona race head from a Japanese singles racer (and rarer than kryptonite) set to go on my bike as the next sensible modification.

What you do with your engine is up to you but one thing you will have to do is grind or machine one of the engine casing lugs down approximately 3mms so the engine fits the frame. DO A DRY BUILD! Yes, it’s a pain in the arse assembling everything twice, but making a test assembly of all the parts before committing to powder coating and plating will save a great deal of grief in the future. The mating ritual between engine and frame should be pretty straight forward, but remember this is a custom bike kit not granddad’s old YZ400, so not everything will line up the first time. Give some thought to your fasteners and engine bolts from this point onward, as some ‘special’ bolts come with the hardware kit supplied by GMC, but a lot of bolts are odd lengths compared to stock TT. I wanted correct length NOS so this demanded a lot of patience at the Yamaha parts counter as I sorted the bits that fit. A simpler option is of course a fist full of stainless bolts but we are building bikes not dairy factories.

OK by now your motor and frame should be mated and glistening on the Workmate, or the Yamaha race stand, depending on your finances. Thought you would be riding by lunchtime, yep, you can be but for oil lines, coil, CDI, foot pegs, steering head bearings…..yep, back to GMC for stainless wide peg kit and back to Yamaha for new lines, you wouldn’t dream of using the daggy dirty ones on your new motor now would you. While you are there you will need a new lower oil line for the lower oil connection to the rear of the frame oil tank. I had my “hose-in-the-van guy” cut and shorten the Yamaha one while he did the rest. Top SR oil line will fit with a bend in it and you will want to run a dual inlet line to the rockers, which are available in kit form. It all takes time to route everything nicely and find the odd little brackets to tie it to the frame, make it look factory and pay attention to detail.

Suspension time - now this can often open a can of worms. You have the old crusty guys and short of leg who favor the old-school 8” option, then you have bigger taller guys like my good self who don’t mind it towering like a block of flats. Forks choices seem to range from the sublime, Yamaha OW, to the ridiculous, DRZ400, but for a budget there are plenty of pre ‘80 YZ forks out there, or if you feel the need them Simons or Fox Forx add a suitable period bit of bling to the project. Out back, again, the sky is the limit, Ohlins, Falcons, YSS, though a little thought needs to go into this as some shocks such as Fox Shox may struggle to clear the frame top tubes. The GMC kit bikes comes with an odd sized headstock, not impossible to find just odd, so time to burn rubber to your local bearing suppliers.

It may seem like a Harley as your HL dream is always a $1000 off being finished, but you are almost there. I went GMC airbox assembly; so on goes pre jetted 38mm Mikuni, NOS carb clamps, airbox in final position and holes drilled in the top frame tab provided to mount it. I made long, odd-shaped 8mm special bolts with 6mm threads in each end to mount one end of the side covers on. Note to self - maybe next time flash a couple of tabs on to the frame for the side covers. Are we there yet? Then mount the CDI to the inside of the airbox, the coil bolts straight on if you pick the right one, exhaust on, YZ125C tank and seat fit like they are made for it. Damn did we forget the wheels?

You can spend a horror amount of cash on wheels if you go NOS rims, stainless spokes and have the whole lot laced up by an individual who knows the black art of wheel building. What has to be raised here is the question of black rims, some VMX guys love ‘em, but I compare them to Makita Suzuki guys with their diamante earrings and hair products. Genuine gold Hallman rims actually came up NOS on Fleabay at a realistic price and on they went. Are we there yet, OK, took a week off work for the final detailing - Husky rear guard, Petty NOS front, cables, YZ levers, RMZ chain buffer and NOS Protec chain tensioner, nice period ‘sponsors’ decals and we are done. Add item number three to the must haves, a plastic kit of assorted motorcycle available for $85 at the bike shop.

So that’s it, Daytona head is still under my desk and there is still room for final detailing but it is essentially done. So what do you get for realistically the price of a new YZ250 or two one year old YZ450s? I guess you get an essentially custom build VMX bike, that like the original TT500 is not likely to show a YZ400 of the same era the way round the VMX track. But it represents, ‘what could have been from Yamaha’, instead we had to wait for the 1998 YZ400F to turn up. Power is realistically like a hot ‘78 TT500 or slow YZ 400 and suspension is easily as good as an RM400 but that is probably missing the point. I look at my HL500 replica as the bike Yamaha could have made that changed the world, they had the potential to build a long travel, three-valve TT540 in 1978, but Yamaha never went there with a balls-out TT500 racer…..but it doesn’t mean we can’t.



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