Tall gearing is probably better than low. The difference between the 654 and the 734 in one video. The 734 is short shifting and maybe 2/3-3/4 throttle. The 734 just does stuff so easy, so unstrained. It also handles 100% better even in a straight line. It actually accelerates fantastic. Wish I'd had this in the 1970s. This has baffled pipes as well. The baffle things bolt in and don't seem to effect power that I can tell. It doesn't struggle to get going.
Ben's race motor will be a 671 90degree. If I put a data logger on the Firebird I can test it better and get data, then swap Ben's 671 in and test and dyno tune it with the data logger, plus put a bung in the exhaust and dial in the carbs. We can go big bore sometime in the future but it will be interesting to see what the smaller size can do.
What I have to do is work out getting oil into the crank. I can see where it comes from and where it has to go but do you use a small spigot and seal Nick? Is it in that case or something outside it?
When Matt drops the engines over, i'll take some photos of the timing cover mods. Its just a top hat for the crank with a seal in it the crank quill can be 8 or 10mm od and 4.5 id pressed in. The pick up at the oil pump end is just a bush, the oil pump bolt has an extended 8mm top with an o-ring which plugs into the bush.
I need to sort out balance weights etc for the offset so i'll email you.
PEH if you look at the video above I posted, that's basically a std A65 below the cylinder head and uses std '70 Firebird pipes mufflers and all, it's 21-47 gears so on a long track it would have legs. Instant grunt and I imagine wheel spin you may be able to control and use in flattrack. Being 650 means it would not hit as hard as a bigger engine and unless you are Mann or Aldana you probably wouldn't want it to. I would not use this frame and heavy stuff, But I expect you do not. If the tracks turn left both pipes are there if you deck it But they are up out of the way. Plus you can just buy them.
Mark, Strangely enough i already have the high front pipes in stock, It does sound well with great pick up on the video i have to say. Our tracks are all short 1/4 mile loose speedway except for Greenfield which is clay so good traction is key. The 750 Trackmaster i recently built has just under 50 bhp and 44 ftlbs of torque and goes well, the owner, rider loves it, he likes the old school 2 left side pipes and mega's, so he had some made in Titainium! more money than sense if you ask me, I will keep the high pipes in mind , i do like the look of them.
Well we have a 'test and tune' weekend at the little circuit on the NSW border 4-5 March.
Although i have all the bits for the offset 750 the crank is not back from the guy doing the balancing so we will run the a10 cranked one. The motor is all together and the gearbox is sorted so it's down to getting jets and timing correct etc. Am a bit disappointed about not being able to get the offset sorted but as the blokes doing the machining etc are all doing it for love, we can't complain. It'll have to wait until i get time to clock up the cam etc and sort the fitting of the 5 speed box in the new late type cases. I measured the compression ratio on this one and it's actually around 11.5-1 so initially i've knocked the timing back to around 31 degs. It sounds very sharp and on the run up the road no pinging and starts well. Lets see if he can break this one?
Just going back to the bearing plate on the trans. No gasket, it needs gluing with super sealer or another gasket type silastic. Two threaded little holes drilled in the seal area and you can wind bolts in and press it off easily.
Hope not....... Crank has outrigger and duplex larger sprocket. G'box outrigger is a press fit, bolts loctited. First head you did for us, the better one is for the offset. Crank is nitrided etc so should be ok to 6800rpm. (on a good day...) We'll see. Found a legal cut slick soft rear tyre we may try. Most run illegal types. We are trying to keep some semblance of the true class on the bike.
I did that on the road. I had a policeman lookin at it up close pondering. I wasn't saying anything. Not worth doing on the road now days, they have some great track tyres that are legal.
Tim's had an outrigger and a steel pin welded up the sludge trap hole which held it together and limited damage, but the pin snapped under the left rod bearing and the spline was twisted. Maybe too much Nitro and boost, I guess. It probably needs a beefier shaft.
He has a normally aspirated 670 drag bike ready to go, which will be interesting. When the blizzard turns into spring or summer over there.
I wish Tim could get some times on my bikes. I'd be highly interested in that.
Recommend to Matt and Damien not to break the outfit on the start line taking off. Hopefully they can just pick em off.
Tim has tackled some problems that are something we can encounter. Such as head gaskets deforming. If it's thin it's no doubt better with less exposed to be pushed. But Tim has it and the cylinder drilled with locating pins between studs. And yes blower and nitro. He's fully into it. But the 670 he has ready will be interesting as it's more like what can be run on the road, at least the engine.
Absolutely gutted that John Hill never got to see and hear the result of his supplied kit in the bike, chasing the guy doing the balancing he says he needs to make an adaptor to spin the crank up, so it'll be done when it's done i suppose. As the forum says, John had been ill for a long while but had generously supplied some kit to us giving hope that we could compete with the cheque book racers out there.
Good weekend up at Stanthorpe, engine went very well but still a few snags with the gearbox (4 speed) Finally located the real problem........ The selector shaft on the early ones uses a key for the stop and spring setup, this was actually a brand new out of the waxed paper item, the bloody key way was about 10 degs. off so the setup could never work properly in both directions. Cure,, remove the key and drill and fit an extra grub screw, job done. Taken me ages to sort this out.
Bloody motorbikes, who'd have one? LOL.
Bloke is still having problems balancing the crank, i gave it to him static at about 70%, told him i want 50% dynamic, he's having problems getting there. Maybe next week now........ Meeting is 4+5 April so the motor that's in it will have to go again.
The old guy who balanced Paul's 744 90 did all sorts of things welding bits on and stuff. Rebuilt and Paul's like, it feels smoother, goes really good, but it still leaking oil. the old devimead cyl is cracked through the pushrod tunnel just below the rear bolts. Waiting for an alloy JH one from EdV. I have castings that would likely cost more to do here. So we are waiting.
It feels smoother with one test ride, much like Ben's so different frames don't do much to effect vibes. I've seen a std one do that long ago, I should have degreased it let it dry and thrown talcum powder on it back when I got it. It doesn't have to run to show up.
You are probably best with what you know and is set up. If it will run without problem it will put you in a good place.
It's right through the tunnel I think. But maybe I could talk to someone about it.
How much stress is on that cylinder just under those two bolts Nick? Would you take it off? I suppose.
The thing is I can fit iron liners in an alloy block, and it's cheap. Or I can have them Nicasiled for big $$. Or get a JH cylinder from EdV which is probably cheaper, unless I just use liners. Liners are probably ok in short strokes but not quite as good or strong. These are thin and press down till they are against a step in the bottom. Ben's using an old linered one and I practiced retaping it to 9mm studs because I considered it scrap. Why they are no good in long strokes is rod cut outs, very slight, and the liner rotating.
Without seeing them it's hard to say but you could always run a couple of through bolts tapped into the fins and the base flange. I've done that successfully before. Just seems a shame to scrap those barrels are they are quite scarce now.
When i used SRM/devimead barrels with my norton crank setups i never needed the barrel cutouts but that was with 6in centre carrillo's so that may have made the difference.