Glen Morgan – NZ
Glen has been a regular contributor to the website, with articles on his bike, building chambers and making racing heads.Here he shares with us some data on his racebike and some pics.
Well, here it is! After five years, three shifts around the country and a few other projects in between.
It’s finished, it’s had a couple of race meetings and it’s about to be moth-balled while I head off overseas for a bit.
The specs are:
Seat, tank, chambers and oil tank by me.
Taper roller steering head bearings.
RS Honda electronic taco.
Forks from a GT 550 disc brake model.
GT550/750 quad shoe front brake.
Brake cable balance box by me. (see pic)
RD250 front guard.
Wheels, standard steel 18 -19 combo on Avons.
GT350 swing arm (4 inches shorter).
Frame braced and shock brackets shortened 2 inches.
Gearbox has oil level modification to 1400cc.
Chain, o-ring on narrower sprockets than standard.
Carbs, standard but overbored to 35mm.
Squish heads at 12.5 to 1 compression (running avgas)
Ignition advance 18 degrees.
Exhausts 182 degees. (widened eliptical)
Transfers 126 degrees (barrel raised)
Inlets 160 degrees. (widened semi-eliptical)
Ignition, total loss with alternater rotor removed.
How’s it go?
Good plenty of mumbo and very quick off the line. There’s a bit of a hole in the middle of the mid-range, but I expect to be able to tune that out as I’ve done nothing to the needles or needle jets yet. The motor is surprisingly keen to rev. The big surprise was that I needed to go to smaller main jets (1.30mm).
It just bogs on anything bigger (standard is 1.50-55 mm). This is not an uncommon phenomenon when carbs are over-bored.
No problems so far. It turns quite well with the short swing arm. It’s fairly easy to lift the front wheel when you get on the gas out of slow corners. The back end steps out if you get on the gas cranked over, but nothing hairy has happened so far.
Fine for drums and will get better with a bit more work. The balance box that I made is probably responsible for this. The original system was a shocker and should be biffed to someone who is doing a road going restoration.
This is definitely a quick bike off the mark – weight forward and hope no one goes down in front of you. The stock box leaves you in a bit of a hole between first and second and you need to watch the revs as you transition, but I expect to deal with that by tuning that flat spot out. After a couple of seasons on modern light weights, I found myself riding it all wrong. Sweeping lines and trying to carry the cornering speed were not the way to go.
Once I was confident that it wasn’t going to do a wild head shake (I hate that!) I found that the time honoured method of stuffing it up the inside, standing on the brakes and grunting away on a tight line was the way to get through the pack. It’s not demanding to ride, there’s plenty of room on it for someone my size (5,11) and it’s considerable physical presence discourages those who would lean on you.
It’s still a heavy bike and I’m tempted to make a lighter frame for it by cutting out some of the tubes and replacing them with lighter ones, but that’s “some when” territory. I will definitely put it on alloy 18s when I get back to doing some work on it. I haven’t gone silly on this bike. It’s pretty much what I set out to build. More than enough grunt to keep an older guy like me happy, comfortable to sit on, plenty of room to tuck down, good ground clearance – generally rider friendly! It’s tidy, without being a show bike, and I might look at getting a fairing and a close ratio cluster.
That will be about it for this one. I’ve got my BSA 500 classic racer project to keep me busy for the next five years!