2013 vintage rules

Yeah, yeah, yeah, but can we brace our swing arms..............

 

and i've still got an XS650 project i'm waiting to pull the trigger on. just gotta get the 'OK' that i can run it in 500GP

 

Hey Sean, just being honest here...but I also recall the DS7 index saying something about pistons...???...."up to 3mm over" or something like that....???

I remember asking David about it, and he said something about thats all thats available..."or sumtin or other", as he would say.

Anybody else recall that?

Just info if you are starting from scratch.

 

yea...just another 2 stroke rule that makes no sence....Can I go 4mm over on my single so I can buy my pistons at my local ducati dealer...................

 

Yea!

 

Really?

That'll get you on the track?

 

cough!

 

DS7 numbers

This is not the same issue Doug. 4 Stroke and 2 Stroke pistons present totally different issues. It is MUCH easier to get a custom billet 4 stroke piston, no such option exists for 2 stroke pistons.

Doug you complain there are not enough bikes on the grid, when someone proposes changes that can add bikes you complain.. I think you just like to complain...

DS7's are piston port motors it has been so long since anyone built a piston port two stroke, there are no bore in replacement pistons available at 54-55mm. Below are the numbers in detail just for reference.

There are 56mm pistons available that fit the motor, they have the correct deck height and ring pin location, they are available up to 57mm

Stock displacement on a DS7 @ standard bore is 247.34cc’s

Based one reads the rules max displacement for the DS7 is either 261.5cc’s (54mm stock bore + .060” overbore) or 263.23cc’s (250cc’s / 54.289 mm bore + .060” overbore)

@ 56mm’s the motor is 266.01cc’s I am certain that the + 2.78cc’s is such an advantage that it will instantly make any DS7 a class killer.

If the oversize versions of the 56mm is allowed up to 57mm’s the motor will be 275.59cc’s. If the 56mm setup does not make the bike a class killer this massive increase of 12.36cc’s will certainly do the trick.

I think the 28mm carb restriction may be a good idea, experience tells me a built DS7 with 28s could get to a reliable low 40 HP range

For the record there are two other pistons that can be used in this motor that will keep it in displacement spec. A Honda and a Suzuki 125. Both require machining modification to the cylinder and/or spacer plates. I believe the DS7 meets the period requirements for the class and could certainly become the class bully within the standard rules if a fully developed one is run and well ridden, the Honda 350 guys would still race each other as they currently do!

Sean will make the right decision, hopefully which ever way it goes maybe we can see some more DS7's show up. Glad to see the TX/XS 500 in V2 I would LOVE to see one show up.

 

....didnt mean to start a mud-slinging contest....but Bob, you do realize 40HP is well beyond a WERA stock 350, right?...its actually closer to a V1 motor than stocker.

In line with your efforts and recommendations for the DS7,...A WERA Stocker Honda 350 has never won the class title.....maybe its time to give them a little more?....maybe 2mm over?

I like the TX/XS deal too.

Where did the discussion about the R5 wind up?

 

I don't think there should be different rules for any one type of bike or person....if you have a problem with my thoughts Bob....talk to me of the bull shit board.................

 

maybe those Honda 350 stockers just look faster than they really are

 

I really am starting to think that the stockers should be allowed the 2mm over GPZ pistons.....but still use stock cams, maintain the no porting and stock carbs.

IMO, It would be in line with what others are asking for.

The CB350 has never won the 350GP title....maybe its time to quit being the red-headed stepchild?

 

40BHP is well beyond a stock CB350 but not a genuine 350GP bike. the DS7 falls into this category. When I first raced with WERA in 2002 Tom Bentley raced one and there have been others as well.

The CB350's were bought into the class just as a grid filler, they were never intended to be serious contenders for the class title. Once you start asking for and getting engine modifications allowed it starts a slippery slope and you can end up with a "shadow" V1 bike and all the expense that goes with that.

 

Robin, your numbers are innacurate, plain and simple....if it was 40, it wasnt stock.....I could see 30-32 for a fresh motor.

Factory manuals say 28. My full on V1 bike was 47.....43-46 for a full on V1 motors are the common. Anything above 45 takes some extroidanary effort. Deans was 44.

A stock CB350 is no where near 40 HP. Just the facts gents.

Look at liperts dyno sheet posted here.....47 I believe. I'll post mine.....these are unlimited mods. Dual plug head. 3.5mm over. high compression. Porting....Buff even uses venturi intake runners and aint breaking 50.

The CB350 has BECOME the grid, period.....lets make it at least equal to the bikes that dont show up!

 

Charlie I said 40 was beyond a stock CB350. Works 350 Ducatis of the late 60's were around 45BHP max, Aermacchis were similar.

In the 80's the 350 class in the CRMC in the UK was full of Ducatis, Aermacchis, Manxes and 7R's, then someone bought out a race prepped 350 Honda, it pretty much killed the class until it was split into singles and twins.

If no one else is showing up and the CB350 has become the grid, why change it? just in case a genuine GP bike shows up and beats them all?

 

I like to see a duck make 45 hp to the wheel.....I have never had more than 30.....now Manxes and 7R's make 50 or so..................

 

30? even with a 350?

 

I would think 40hp from a piston port DS7 means a really really narrow power band...