G3l hot rod???

[Rickdiculous]

Hi all, I recently got a basket case 46/ g3l. I am planning to make a bike to take to the Bonneville salt flats and compete in the vintage 350 class. What are some performance mods that would help to pep up the old 350. Are there cams available, bigger valves, mikuni, exhaust????? Would a later model head bolt on? This is my first matchless so bare with me and excuse my lack of knowledge.

[clive]

No replies because I guess most of us in the club would not have tried anything like this. I am guessing you could use the later higher lift cams if you machined the timing side case to allow the proper movement in the tappets. The 500 had a bigger inlet valve so you could fit that if you opened up the inlet track. 500 exhaust is bigger. No idea about Mukini carb. The later aluminium heads had different valve springs but could be converted back to coil springs I think. I think, but I am not certain that the later ally head would fit the barrel but unlike the iron heads there was a valve seat set in the aluminium. Therefore if you went to a larger inlet valve this would be a problem. Using a 500 cylinder head would I imagine lower the compression ratio.

[Rickdiculous]

Thanks Clive. seems like if i could fit the later model head that might be an improvement. the 500 cams soung like a good idea also as long as i could figure out the cam timing. how about a good source for parts? it is slim picking for these motors here in the u.s.

[dave16mct]

You could try Mike Partridge at Waldridge Motors, Toronto.

https://www.walridge.com

Dave

[clive]

350 and 500 cams were the same but with different engagement with the small gear. You could just try changing the timing of your current cams. The later high liftcams (marked H) will not work unless you machine more clearance on your crankcase for the tappets. The small timing gear has a dot on it which should coincide with TDC. timing the cams is easy but you could try playing with the inlet timing to get more fuel in.

[Triumph-Legend]

I'm running my 1950, 350 comp motor with standard compression and SH cams. Cracking performance, pulls pretty hard for a 350 and flies. Will easily run with a 500, yet still nice a tractable in the woods. The iron barrel motor is basically the same motor, although different stud spacing.
Lucas comp mag gives a nice big spark and I changed from the Amal 276 to a Monoblock carb. Inlet port cleaned up and do check that the carb and spacer block blend in nicely with the inlet port. Bottom end has had all the crank bearings replaced. Do no use a one piece crank pin. It will break.

[Rickdiculous]

Triumph-Legend, that sounds great. are the SH cams later?my cams have no markings, with out too much fiddling could i fit these into my 46 g3L. also which crank pin do you reccomend? alpha? thanks in advance.

[Triumph-Legend]

Triumph-Legend, that sounds great. are the SH cams later?my cams have no markings, with out too much fiddling could i fit these into my 46 g3L. also which crank pin do you reccomend? alpha? thanks in advance.

I'm sure that the cams fitted into your motor will be the standard cams, These were used up until 54 when the HL, (high lift), cams were introduced onto the road bikes. The old, pre 54 cam timings were and still are often preferred by trials riders as the produce a soft power from the motor.
The SH cams are the comp scrambles cams. To be honest I'm not certain when the SH cams were introduced perhaps somebody else can give a definitive date. Speaking with John Bolton recently at workshop 14, he did mention that there was a company reproducing the SH cams. Note, you will need to relieve a small piece of the inner timing case to fit HL or SH cams into the earlier motor. I'm waiting to see how the 'new' SH cams work in a G80 motor that John is working on before considering a pair for my 53 G80.

Crank pin. All of the old one piece crank pins should be cleared out by now. Either used and broken, as happened to me, or thrown away. So the big end assembly that you buy should be the two piece crank pin. But do check before fitting. The one pin crank pins can snap very easily, I think that the incorrect, 'old stock' big end fitted into my motor lasted a few weeks before snapping.

If you can get hold of a Lucas competition magneto, grab it. The points setup is a lot more sturdy and consistent than the standard N1 setup.

[raffles]

SH cams are available from the club sparse
Tony

[Triumph-Legend]

SH cams are available from the club sparse
Tony

I may be knocking on their door for a set of those cams.

I see there is no mention on the original post of the fuel allowed for the run. Many years ago I did a deal to clear out a blokes shed and acquired a BSA single sprint bike running on Nitro and fitted with a brass carb. Also included was his track bike a tuned up Enfield twin with a Dellorto SS1 carb, and loads of spares. I kept the Enfield, then sold off the BSA. As I was clearing out the shed, the seller gave me lots of tins of Castrol R and said don't forget that 5 gallon drum, you will need it for the Beeza. That was a tin of fuel for the bike. The friend I sold it to broke several rear chains testing, then the barrel fixing studs came loose. With the engine sorted and a very heavy new chain he put in a few good test runs. The bike was eventually crashed when a rear frame tube broke. I have no idea what became of the bike once repaired. Ah, golden days.

Tuning up the old motor is not a bad idea really, Dig out the old 'Tuning For Speed' book by P. E. Erving, for a bit of a refresher course on tuning old British singles.

Hmm, Replace all the crank shaft bits, axles big end and bearings. Maybe lighten the flywheels a bit, polish and rebalance. Will a nicely polished CS rod fit this motor? Over size barrel base studs. Well ported head. SH or better cams. Later valves without the stem caps. Possibly larger on the inlet side. I think I would rather trust coil springs on the valves. Quality springs, probably with inner damper spring. I think I would try to use the original iron head. Why not? keeps cost down and easy to work on for porting and skimming. If an ally head falls in your lap cheap, then OK use it but the old head will give you a good idea of what works best. Do not go too high on compression. Why risk a melted piston or busted big end. To win or get a result you need to finish, best not to DNF.

Nothing wild really, just a good clean rebuild, should not work out too pricey.
As ever all transmission parts optimised to run true, reduce friction and give positive gear changing. Cycle parts are obvious really, lighten and throw away anything not required. Rigid frame with pegs at the rear and bars set down near the bottom yoke, (do fit a fork brace), maybe a couple of tube fuel tanks set either side of the top tube. Should give a nice laid down riding position. Wheels and brakes, just lighten the parts that you have. Use a very simple primary chain cover, makes gear swapping a lot easier and you won't need to run the clutch in oil anyway, plus the extra clearance will allow the use of stronger primary and final drive chains. Yeh. Go for it. It sounds like a lot of fun.