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Myles Raymond
Myles Raymond
Glasgow, Scotland
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Allan G, gavin eisler, Mark Parker, pushrod tom, Semper Gumby
Total Likes: 7
Original Post (Thread Starter)
#852428 06/25/2021 11:33 PM
by DMadigan
Printed ports to try on the flow bench.
[Linked Image from]
[Linked Image from]
34mm Koso Oko, Ford Ranger valves
Liked Replies
#852695 Jun 29th a 10:19 PM
by Allan G
Allan G
Originally Posted by DMadigan
You could say a bit advanced charging. The GSXR1000 generator is rated at 400W at 5000 RPM by sources that I could find.
The white outline on the left is the 6005 bearing and GSXR stator mount. The stator face of the A65 case has to be lowered by 0.41". Obviously easier on the earlier models with the removable stator mount or the studs alone mount. Easy enough to reverse with a spacer.
Yes, one 16005 in the outrigger but where is the other one?

All interesting stuff. Mark has two outriggers. One on the crank and the other on the gearbox mainshaft. (Sorry it’s a short and sweet reply, bedtime here). Hth
1 member likes this
#852856 Jul 2nd a 05:20 AM
by Mark Parker
Mark Parker
Just arrived from MAP in the states. Delivered to the door Friday today after ordering last weekend. So apart from some other nice stuff a few valves.

These are the nitrided stainless swirl pattern inlets 42mm and std nitrided exhaust valves. Why they are good is because with a K-linered guide they can be fitted fairly tight reducing wear. And when they do eventually wear out they can be lined again without removing.

(pictured are actually the big exhaust valves. I have them in the Firebird but std exhaust valves in Matt's winning sidecar. So the only reason to require bigger exhausts is worn seats or using a blower, according to Vizard.)

[Linked Image from]

The beauty of this set up is it fits straight on a stock 650 bottom end. The calculator predicts over 70hp but that remains to be seen. Seems no problem with piston to valve clearance, just needs good springs set to the correct fitted length. Nice on a stock 650 and enough flow for possibly a predicted 82-87engine hp on a 750 race motor.

I may be able to fit the steel rods before I can get it on a dyno. And hopefully have it balanced smoother at higher rpm. But it's a bit hard to get motivated to pull something that runs nice apart.

This shows how the 34mm id tube is squashed and lined up, Then the tags just welded on. The oval is right out to the 1/4"unc screws. I just fit helicoils in the holes.

[Linked Image from]
1 member likes this
#852926 Jul 3rd a 01:02 AM
by Mark Parker
Mark Parker
This is a XR750 port it's wider than I can fit, but like I was trying to say even the 883cc engine would be pushing the rest of it to use the flow. I ran it on the dyno as it was which was over 14.5-1 lean at max rpm and leaner before that, it needed to be 12.5 for max hp. The operator was surprised at 85rwhp first run but we ran a few more runs and got graphs to 83 but he said take no notice of these because it's two points too lean. And pointless moving the timing. What it may give with a bit of fiddling could easily be more which would take it over 100hp at the engine, he also wanted to run 1000rpm more to see when it would stop making power. But we were just about at 8,000 already.

[Linked Image from]

Longer rods in that engine would make it better, stronger, but it's my road bike and the crank is .050" under and I don't know what is the next weakest bit.

The bike is also lighter than the firebird and is barely ticking over going pretty fast. Ben's 750 is really nice because the motor needs no rubber mounts is easier to kick and you rev the engine more. The head on it is similar to the 883 but flows a bit less. For enjoyment of riding it's really nice. But if the head we are going to swap on with 34s makes for a stronger midrange it's pretty pointless going bigger cc. The 883 has heaps of grunt and if the 750 can be closer, it can also rev more. And fits the cases and space much easier.
1 member likes this
#852945 Jul 3rd a 07:30 AM
by Mark Parker
Mark Parker
With an unmachined casting those holes would not be drilled. 9mm studs seem trouble free. I put bearing blue on the head and bolt it down minus gasket then sand the high spots. Did the same with the unmatched cases measured to the bearing holes to get them square with a file. No leaks plenty of compression frown

I can run 12.3 or 11-1 depending on one or two head gaskets. Too chicken to run just one with this head. Never had such good response. And it did spit me off once though not being careful with a cold tyre. Being dumb would be another way to describe it. Sort of fixed the old fairing and got a better one.

[Linked Image from]

The thing is actually idling in this photo.

[Linked Image from]
1 member likes this
#853043 Jul 5th a 08:48 AM
by Mark Parker
Mark Parker
Just fixed this tiny little port so it's smooth. This is with std valve calibrating off the std port which is around [email protected]". This head must be earlyish because these ports measure 29.5mm not 30mm. @ 28" the std port needs 3 vaccs the modified one needs 4.

So through a stock 30mm Concentric it's about 143cfm @ .385" and about the same @.350". The stock side is probably around 105cfm through that carb. Just the port is 146.66 and with an old bell-mouth 150. So again the carb takes a bit off. But this might be good with a pair of std GPs on a Spitfire. Though a good bell-mouth with no gauze on the 30mm Amal might do the same and be easier to live with.

My thought with this head was to make it a better breathing head that can use the stock GP carbs on a Spitfire, and make it perform noticeably better. I'm just thinking of selling one and advertise it on E-bay as a ported Spitfire head to suit GPs. Because it sounds a bit more special than Lightning head.

I just want to make sure it's a noticeable improvement if someone buys it so they are happy with it. I guess I should measure speed but I can guess its similar to the 34mm port.

[Linked Image from]

The reason to test with a bell or radiused entry is to take the effect of the sharp entry away. Otherwise you can change flow quite a bit by accidently making that sharp edge a bit rounded. Having the carb on takes that edge out of the calculation and works better as well. On these figures it should give a good hp boost, but you don't know what people will do setting stuff up. If it gets near 70 engine hp it would be good.

[Linked Image from]

Last time I tried this size port it was 137.5cfm just the port so 146 is pretty cool.
1 member likes this
#853170 Jul 6th a 11:17 PM
by NickL
The Weber books by Passini i have show revs/main venturi diameter/cc guidelines
for both single and multi cylinder setups fed by a single venturi. I know they are
probably old school now but he says in the text that they are guidelines not gospel.
Actual choke size is shown as being related to RPM more than anything.
I knew lots of blokes who fitted large carbs onto bikes and removed them later to regain
lost performance, both at the track and on the road.
The ideal carb for everyday type use tended to be a twin choke progressive type,
giving cost effective overall performance.

1 member likes this
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