Cams stg1

[Roger Ditchfield]

Hi Carl. Thank you for your kind wishes and I am having a great time with family here in AU although it is pretty hot some days as you will have seen on the UK news.
The performance kit that Bill is offerring now uses re-profiled OEM cams which are milder than the Moriwaki ST1 cams and the pistons are either Moriwaki 10.6:1 or JE 11.5:1. He told me that he doubts if he will do many more engines for the AU guys if any.
I have a great affection for the VTR and I too are sad to see it disappearing from the roads which is mainly due to the lack of affordable performance parts as the manufacturers deem it uneconomic to produce them. I persuaded Moriwaki to make one more production run of the piston kits and when these are gone (which they nearly are) there will be no more. JE are in exactly the same position, when current stocks are sold there will be no more. Both manufacturers will produce a special batch for me with a minimum order number of 100 sets!!! I can still get C/Fibre and FRP race/trackday equipment from Japan ie the fairings, cowlings and the ram air airbox and side tubes but again this is expensive and to be honest it is only for the real enthusiast as it makes no economic sense to convert your bike this way unless you want to keep it as a "one off special". So as you say performance enhanced VTRs are being confined to history which is a pity as I could make some great bikes. The SP1/2 (RC51) are following close behind although there is a slightly bigger market in the US. If this trend continues I will have plenty of time to write my memoirs or at least an obituary dissitation on the VTR !!!

[gl_s_r]

As a question why do people go the higher compression route rather than oversize when they change the pistons?

As a theoretical question what would be the maximum oversize bore (assuming you could get the pistons etc.) you would get with the standard block and what capacity would it give you?

Roger: can I ask the difference between stage one and stage two pistons.. and are they only dedicated to their own stages, for example if someone sold a set of stage one cams and a set of stage two pistons would they still go together?

[benny hedges]

High lift cams and high compression pistons with raised crowns wouldnt be a wise move lol
Also, for the road, there comes a point with high compression that the motor becomes so lumpy its unrideable, especially with a lightened flywheel....

The storms liners are only about 8mm thick so realistically, going beyond a 100mm piston would mean resleeving.. though at 100mm the options are a bit wider with manufacturers like pj and wiseco offering pistons, as well as the porsche alternative....

But then you have the rear sa mount to consider with all that extra power.... And at that point maybe your money is better spent on suspension, braking and lighter wheels and bodywork...

[Roger Ditchfield]

HRC and Moriwaki only made one profile of Hi-Comp piston. People who refer to ST2 pistons generally mean JE, Wiseco etc whose pistons are above 11:. You can use 11:1 piston with ST1 & ST2 cams (if you can find any ST2s). However, to be sure whenever you use Hi-Comp pistons with Hi-lift cams always check the Piston Valve clearance -MINIMUM INLET = 1.2mm EXHAUST MINIMUM = 1.5mm. There is more clearance to play with on the VTR engine compared with SP1/2 in this area and often you can shim the head on the VTR after installing HI-Comp and Hi-Lift options to maximise the output to bring the P/V clearance down to the above figures.
In answer to another point people try to use the standard bore if possible as this leaves the option to re-bore should a problem occur at any time in the future. Trying to find oversize pistons (past 100mm) with the correct/suitable crown profile is almost impossible unless you commission a large batch of pistons to your specification from a manufacturer. Too high a compression ratio achieved by high crowns in practice is self defeating as it affects the "flame-over" speed or the valves have to be pocketed too deeply for efficient gas flow. I would never use greater than 11.5:1. The "window" of real usable power is quite narrow on the VTR and extremes of equipment generally prove inaffective. A fine balance of many components from the air intake to the exhaust tail pipe is what actually works to produce a powerful rideable VTR. As mentioned by Benny attention to the suspension whether the bike is Street,Trackday or full Race bike is of great importance to produce a well balanced machine.

[thumperslaw]

Has any one cracked open a duke motor and seen the pistons in that? Or fitting sp-2 pistons

[benny hedges]

Pin diameter is differrnt on the sp.
Porsche 3.2l pistond will go in

[tony.mon]

Question re oversize valves....
I can get oversize valves, but what machining needs to be done in order to fit them?
The seats don't look thick enough to machine out +1mm; as you'd lose .5mm off each side and they're not thick enough to leave sufficient meat.
Can you just obtain 1mm oversize seats and have them pressed in?

If so, I'll have a go and see what, if any, difference it makes.

Luckily the valve springs are ok with standard ignition ecu revs,- you won't get valve bounce before the hard limiter kicks in.
A nice set of Ti collets would be good, though.

[VTRDark]

This may be of relevance Tony. There's also some specs on various cams, not sure how accurate they are though. Maybe Roger can confirm.
http://www.superhawkforum.com/forums/mo ... lves-7883/

Something else that appears to be quite common over the pond is to angle the valves slightly different in the seats while porting, IIRC something about a 3 angle valve job. Have you heard anything about this.



(:-})

[tony.mon]

This may be of relevance Tony. There's also some specs on various cams, not sure how accurate they are though. Maybe Roger can confirm.
http://www.superhawkforum.com/forums/mo ... lves-7883/

Something else that appears to be quite common over the pond is to angle the valves slightly different in the seats while porting, IIRC something about a 3 angle valve job. Have you heard anything about this.



(:-})

That isn't changing the angle of the valve, it's how many changes of angle there are on the seat when cut.
The ideal valve to seat is a knife edge, because that allows the most gas to flow through. But it would wear very quickly, and you'd have to reshim the valve clearances often.
SO you have three angles cut into the seat face, which is a good compromise between the two.

If racing, and you don't mind reshimming valves more frequently a five angle seat might be worth considering.

[Roger Ditchfield]

Tony, I am able to facilitate the recutting/reseating O/S valves INL = +1mm and EXH = +0.5mm
Who is making the O/S valves if you do not mind me asking?
In answer to Cybercarl's posting, the info regarding valve timing specification on the Superhawk site is correct

[tony.mon]

Tony, I am able to facilitate the recutting/reseating O/S valves INL = +1mm and EXH = +0.5mm
Who is making the O/S valves if you do not mind me asking?
In answer to Cybercarl's posting, the info regarding valve timing specification on the Superhawk site is correct

PM'd, Roger

They're 1mm oversize both ex and inlet, btw.
There's only a few left, so I'm keeping the source to myself until I've bought mine and Yeti's, but if there are any more left I'll happily share.... You know how it is, I don't want to be left without any for myself!

[Roger Ditchfield]

Hi Tony. I fully understand you wanting to protect your source- it is not a problem. However, I do have a real concern regarding 1mm oversize exhaust. All the R&D and Circuit testing by HRC, Moriwaki, the late Bob Hayashida and myself concluded that +0.5mm oversize exhaust produced the best results. I am checking the current 2013 UK prices and will be able to quote accurate prices for valve cutting.

[gl_s_r]

Is it just me or do most people love a comprehensive reply like what I reading. More so with the ability to pop names in the conversation like the post previous to back up your opinion.

Roger, was there ever experiments in different types of materials when doing your trials such as titanium valves, con rods etc or do you you may have missed out on that side of things as there wasn't the easy ability of things like DLC coatings readily available?

[tony.mon]

Hi Tony. I fully understand you wanting to protect your source- it is not a problem. However, I do have a real concern regarding 1mm oversize exhaust. All the R&D and Circuit testing by HRC, Moriwaki, the late Bob Hayashida and myself concluded that +0.5mm oversize exhaust produced the best results. I am checking the current 2013 UK prices and will be able to quote accurate prices for valve cutting.

That makes sense, Roger- ties in with cam profiles, too.

As I understand it, the ex cam profile is fairly efficient; it's the inlet side that holds these engines back.
Not surprising given the carb throat and tract sizes, and it seems fairly marginal getting these size carbs working effectively across the whole rev range.

Singles and twins seem to be more of a challenge to tune for the lower part of the rev range- simply because it's the lower revs that are used more often and contribute more to the overall experience of using the engine, compared to an IL4.
With IL4's there isn't as much usable torque, so you don't use it as much as you would with a twin or single- you're less reliant on it's performance in this section of the rev range, so it's less of a problem if it isn't fuelled perfectly.

With IL4's it's all about top end, really, with less emphasis on low end performance, singles and twins are the other way round.
One gets you out of a corner quicker, the other gets you to the end of the straight quicker....

Back to valves- I'l see if the company has any .5 oversize ex valves, otherwise in the absence of these I'll just fit the +1mm inlets, I think. Not perfect, but should still improve things a little.
Price for the head work is the missing jigsaw piece for this project atm.

[Roger Ditchfield]

Hi Tony. IMHO you are better using OEM exhaust valves with a little mild porting than the 1mm O/S valves. Your analysis of the relative performances of Singles, "V" twins and Il4s is absolutely correct. I cut my teeth on G50s and Manx Nortons and got them pretty quick so I had an advantage over younger tuners when it came to the VTR. Out of interest the piston speed of the VTR at 9,200rpm is the same as the G50 and many other similarities allowed by past experience to play a significant part in tuning VTR. I will get back to you as soon as I can over 2013 pricing for valve cutting and all other aspects of cylinder head work that may also be of interest to other guys on the Forum.