107 rod to 110 ?

[eden]

This is a bit confusing. IMO the only way to use a longer rod to get it to make more power would be to raise the barrel so the port timings are a little higher, however if he does this then he will have to have some taken of the top of the barrel or his squish will end up too big, and in any case this could be achieved with the current rod.


Bonkers

[slangen]

They must have sold hundreds of these kits already, someone on here must be running the kit and can tell their honest opinion about performance. I have spoken to a few people that have the kit and they are confused what to expect like you. Did the scooterotica team not set up one of these recently, don't know the stroke they used. Good luck!

[jason frost]

This is a bit confusing. IMO the only way to use a longer rod to get it to make more power would be to raise the barrel so the port timings are a little higher, however if he does this then he will have to have some taken of the top of the barrel or his squish will end up too big, and in any case this could be achieved with the current rod.


Bonkers

Why would you need to take anything off the top with the 110?

[jason frost]

They must have sold hundreds of these kits already, someone on here must be running the kit and can tell their honest opinion about performance. I have spoken to a few people that have the kit and they are confused what to expect like you. Did the scooterotica team not set up one of these recently, don't know the stroke they used. Good luck!

I'm running one and have fitted afew , most have gone from a Mugello to the RT and they say the RT has more power.

[Rich_T]

Assuming the barrel height is adjusted to return the same squish as the 107 rod then there is a marginal improvement in the geometry between the force from the piston being transferred to the crank pin rather than the cylinder wall. The port timings will change, the effect of this is best studied through a port calculator.

There is always a debate about pumping efficiency, IMO there is a lot of subjective stuff and some many variable between set ups it makes it very hard to make a subjective comment. Will it make a difference of 1-2bhp? It might but I doubt it would make 5-8hp difference for example. It is up to you to weigh up the benefit/cost ratio.

If the new crank is a true full circle then there will be a benefit as the drag will be less and this should help power at the top end but this benefit is not dependant on the rod length.

[Yanker]

Assuming the barrel height is adjusted to return the same squish as the 107 rod then there is a marginal improvement in the geometry between the force from the piston being transferred to the crank pin rather than the cylinder wall. The port timings will change, the effect of this is best studied through a port calculator.

This has me baffled (yet again). Please indulge my unrefined mind: why would a difference in rod length alone with the returned squish (IE. with a 3mm base packer) return any different por timings to 58/107?

The rest of the 'pumping efficiency' is a far more complex study of TDC crankchamber volume (with the inlet tract resonance factor), blowdown, port time area, exhaust pulse efficiency, port angles/piston crown profile, cylinder head volume, squish and squish velocity. surely forgot more factors than I can remember there tho.

The rod length difference has me baffled unless it referes simply to manufacturing tollerence differences and getting the RT Kit timings simply on spec (suspect this may prove to be the case).

This crank 'windage' factor is only somthing I have heard Richard T propound in favour of HPC (or at least low COD ) webs ......

[boris]

I would have put the link on from MB's RT face book page. where MB commented on my set up suggesting the longer conrod. But it seems to have vanished of his page.


Sent from my HTC Sensation Z710e using Tapatalk

[Mark ULC]

Know little of tune set ups but can cut and paste : below is from MB web page;

MB also recommends using crankshafts fitted with 110mm con-rods this allows the Race-Tour kit to become fully adjustable to suit all engine casings, as they all alter in machined heights. You can use a standard type crankshaft with a 107mm rod but these have limitations based on the only adjustment is using a base gasket or not, only allowing raising the cylinder and port timings by 0.4 - 0.5mm which can limit adjustment on the squish clearance. With all cylinder kits we recommend using our high tensile cylinder stud kit, MBgm cylinder stud kits come with the MBgm Race-Tour cylinder kit, if you do not use these could face problems later on with stretched or snapped studs.

You can use any combination of 58, 60, 61, 62, 63 or 64mm crankshaft with the Race-Tour kits, using either 107, 110mm or 115mm con-rods used in conjunction with our long or short crown height RT pistons to develop the cylinder kits even further. Unlike all other kits no extra machining or mods are required to set up the Race-Tour cylinder kit. (except the exhaust port needs raising on longer 61, 62, 63 and 64mm stroke crankshafts and maybe a head may need machining to suit these longer cranks)

To set port timings correctly use what ever combination of cylinder base gaskets or alloy cylinder packers to get the piston level with the lower edge of the transfer port at BDC (bottom dead centre), this should set the piston 0.5 – 1.00mm above the lower edge of the exhaust port. This is where the port timings are designed to work for all round road touring. You can adjust the cylinder by raising it so the exhaust port is level at BDC with the piston this will improve higher end power and increased revs.


You guys with knowledge can comment. My RT225 uses the 107mm but cannot advise on squich etc as it was set up by Dan at Scooterotica.

[Rich_T]

Assuming the barrel height is adjusted to return the same squish as the 107 rod then there is a marginal improvement in the geometry between the force from the piston being transferred to the crank pin rather than the cylinder wall. The port timings will change, the effect of this is best studied through a port calculator.

This has me baffled (yet again). Please indulge my unrefined mind: why would a difference in rod length alone with the returned squish (IE. with a 3mm base packer) return any different por timings to 58/107?

The rest of the 'pumping efficiency' is a far more complex study of TDC crankchamber volume (with the inlet tract resonance factor), blowdown, port time area, exhaust pulse efficiency, port angles/piston crown profile, cylinder head volume, squish and squish velocity. surely forgot more factors than I can remember there tho.

The rod length difference has me baffled unless it referes simply to manufacturing tollerence differences and getting the RT Kit timings simply on spec (suspect this may prove to be the case).

This crank 'windage' factor is only somthing I have heard Richard T propound in favour of HPC (or at least low COD ) webs ......

Port timings DO change with an increase or decreases in rod length, this is because of the trigonometry created by crank stroke/angle and rod length. The effect on timing vary depending on the lengths. As I mentioned before, play around with some numbers on the port calculator on this site and you'll see what I mean (the values between 107 & 110 are very small but there can be compounding effects with stroke changes too). The bigger effect IMO is the geometry of the piston force acting on the crank pin/cylinder wall, again this is trig.

Low windage/drag is important, if you take yourself out of the scooter arena and look at other engines from MX, street racers and karts you'll find the vast majority (and every kart engine) have plastic stuffers of some description. This is not for balance, it is for low drag in the crank case the karts even have knife leading edges on the con rods to reduce drag from con rod movement (that feature would have nothing to do with HPC).

[eden]

This is a bit confusing. IMO the only way to use a longer rod to get it to make more power would be to raise the barrel so the port timings are a little higher, however if he does this then he will have to have some taken of the top of the barrel or his squish will end up too big, and in any case this could be achieved with the current rod.


Bonkers

Why would you need to take anything off the top with the 110?

because if he set it with the same squish that he has now which is good he would have nearly the same timing, it would be about .5 degrees different. im assuming the head had no gasket. if it does then yes he could remove the gasket or use a thinner one. do these kits use head gaskets?