Is there any interest in High Ratio Primary Gears

[riksoto]

Looks like 4437 RPM at 75MPH with an 18/40 sprockets
4660 RPM with 18/42 sprockets
4881 RPM with 18/44 sprockets

this is with a 130/90-16 tire

Riksoto

stock RPM is 5012

with the MikesXS OD 5th gear
Sprockets RPM
18/40 4253
18/42 4466
18/44 4678

 

[TwoManyXS1Bs]

Hey, riksoto! Count me in!!!

 

[riksoto]

I need 5 people to make the order. I hope to have a few more soon so I can get them for the winter builds.

V/R
riksoto

 

[Okie]

I would like to get a set as well riksoto. Interested in hearing about your clutch mod.

 

[riksoto]

I am working on a prototype clutch now and should have it up and going this summer.

V/R
Riksoto

 

[650Skull]

Can't see any reason for mikes 5th gear overdrive if a set of racing primaries are installed, defeats the purpose of spending all that money

The racing primaries transfer the load from the gearbox to the motor, (crank), means shifting into and changing gears is made easier. Shouldn't be a need for any mods to the clutch due to the load shift to the engine.

 

[riksoto]

Can't see any reason for mikes 5th gear overdrive if a set of racing primaries are installed, defeats the purpose of spending all that money

The racing primaries transfer the load from the gearbox to the motor, (crank), means shifting into and changing gears is made easier. Shouldn't be a need for any mods to the clutch due to the load shift to the engine.

You are 100% correct!!!
When the load is placed on the engine the clutch speeds up 115 rpm at idle and 478 rpm at 5000 rpm.
The oil drafting is increased by 20%. That increases oil temp, breaking down the oil faster and it can't do the right cylinder any help.
By changing the clutch design and adding an extended oil sump the drafting is greatly reduced and is worst in a tight right turn, dropping the oil temp, right cylinder temp and reduced drag freeing up HP to the rear wheel.

One other reason for the new gears is to reduce the stress on the crankcase. The crankcases have been known to crack when overbored and cammed for max effort 80+ HP.

The info posted for the OD 5th gear was for those who already have one installed or may be interested in that option.

However there are other reasons to change a clutch design.

1...Reduce weight
2...Faster acceleration
3...Easier operation
4...Reduced inertia
5...Easier shifting
6...Reduced oil drafting (lowers oil temps and right cylinder temps)
7...Modern components
8...Better pressure plate retention
9...Better pressure plate design

This clutch is being designed to be used on bikes from mild to wild and stock primary gears or high ratio gears. I will post results as soon as possible.

V/R
Riksoto

 

[650Skull]

80hp is a lot. May lead a race for a lap or 2 before she blows, lol.

From what i understand 72 HP is the mark that is reliable and cases are safe.

Scroll down to the article Craig Weeks writes about on the best hp for the XS650 engine

 

[riksoto]

80hp is a lot. May lead a race for a lap or 2 before she blows, lol.

From what i understand 72 HP is the mark that is reliable and cases are safe.

Scroll down to the article Craig Weeks writes about on the best hp for the XS650 engine

Once again you make a good point on th HP side of the equation, but this is RWHP with stock primary gears. Let's change the gears and by doing so reduce the engine sprocket torque by 20.5% allowing us to increase the engine HP(if my math is correct close to 90hp to the wheel) without changing the torque transmitted by the stock gears through the transmission and making it up on the wheel sprocket. Speaking of wheel sprockets, this allows more sprockets to choose from depending on the state of tune and engine builds.

That being said what about the heat, drafting, friction, inertia, reliability, availablity of common parts, and ease of use w/o hydraulics which are always a goal for an XS Enthusiast.

All of the benefits listed above and the release of a few ponies in the process, what is wrong with that?

V/R
Riksoto

 

[XSLeo]

I think if some one could extend the Mike's over drive so 5th gear is a two tooth change, 4th a one tooth change, 3rd left alone, 2nd a one tooth change and 1st a two tooth change would prove very good for street purposes.
The gear ratios are too close, a wider range would be much more useful.
That I would pay $700 for.
Leo

 

[riksoto]

Thank you for the renewed interest in the gears. I just need a few more commitments to put in an order. At that time I will require full paypal "GIFT" payment so there is a record of the purchase and protection for both of us. This is my second order and I had conducted the sale the same way. Once again thank you.

V/R
Riksoto

 

[650Skull]

If proven experience is dismissed by throwing around a few equations then I'm sure you'll get some takers.

Check out the Aussie site and Ivan has improved his high ratio primaries with roller bearings. less friction so more hp to the rear wheel

 

[riksoto]

I think if some one could extend the Mike's over drive so 5th gear is a two tooth change, 4th a one tooth change, 3rd left alone, 2nd a one tooth change and 1st a two tooth change would prove very good for street purposes.
The gear ratios are too close, a wider range would be much more useful.
That I would pay $700 for.
Leo

The 1st to 2nd gear ratios of a 1970 transmission are better than the other years but the rest og the gears are the same ratios.

V/R
Riksoto

 

[riksoto]

If proven experience is dismissed by throwing around a few equations then I'm sure you'll get some takers.

Check out the Aussie site and Ivan has improved his high ratio primaries with roller bearings. less friction so more hp to the rear wheel

Thank you for the info. The new gears will have needle bearings as well.

I may have appeared antagonistic, that was by no means my intention. I have no arguments with the info you have provided, just a different way to look at the same info.

I am attempting to give more options to those people that may want to see how much can be squeezed out of the XS or those that want to have a better selection of clutch fricion components and ease of use.

V/R

Riksoto

 

[650Skull]

Thank you for the info. The new gears will have needle bearings as well.

I may have appeared antagonistic, that was by no means my intention. I have no arguments with the info you have provided, just a different way to look at the same info.

I am attempting to give more options to those people that may want to see how much can be squeezed out of the XS or those that want to have a better selection of clutch fricion components and ease of use.

V/R

Riksoto

My problem with this thread, your statements in answer to my queries seem flippent.

You have never posted anything about you or your mechanical experience regarding XS650's or bikes in general, or any engineering experience. In fact there is nothing in you handle or any introductory post about you what so ever.

Advising members to buy 40 and 42 tooth rear sprocket to couple with the "High ratio Primaries" goes against any information i have learnd about these gears. Claiming a better designed clutch will make the "high Ratio Primaries" work better on the XS650 also goes against the information I have.

This info is from an XS650 Racer and he is regularly in the top 3 in his class in his races and often has won the class at the end of the meet when the points are totaled. He has been around these bikes for a long time and i will take his information seriously, and yours not so.

I would caution any one using the stats and information posted throughout this thread without doing some research for confirmation sake.

 

[TwoManyXS1Bs]

I've been wanting this since the mid-'70s. So, trying to research this, pull all the data into one posting, and counting gear teeth 'till my eyes are bleeding.
Here's what I've found so far in 'high ratio' primary gearsets:

Pic #1 - Australian Ivan Hoey's 32/69 gearset, copy of Tony Hall's Halco design. With roller bearings.
From the XS650 Australian Club website: http://www.xs650.org.au/Racers.htm


Pic #2 - Comparison of stock 27/72 primary gearset to the 32/69 gearset.
Pic supplied by 270Yam.


Pic #3 - Heiden Tuning's offering, advertising a 35/80 gearset, but the picture shows a 32/69 gearset?
From Heiden's website: http://www.xs650.biz/p/36/mo74-cg|29=1


Pic #4 - Riksoto's primary, shows a 32/68 gearset. A different geartooth combination. Hard to see, but looks like maybe a slightly larger diametric pitch is used?
Pic supplied by member Hamos (post #15).


Pic #5 - Required clearance grinding of the right side engine cover, to clear the larger engine gear.
From the XS650 Australian Club website: http://www.xs650.org.au/Racers.htm


Gear ratios are usually referred to as input/output speed reduction ratios, but that creates an inconvenient number, so street convention for vehicles usually inverts the ratio, makes it easier to understand, especially if you're more concerned about torque multiplication (for drag racing) than output speed.

Using these primary gearsets teeth counts, sorted in increasing speed ratios, we get ratios of:

Stock --- 27:72 - speed ratio = 0.375, torque ratio = 2.667:1
Heiden - 35:80 - speed ratio = 0.438, torque ratio = 2.286:1
Hoey --- 32:69 - speed ratio = 0.464, torque ratio = 2.156:1
Riksoto - 32:68 - speed ratio = 0.471, torque ratio = 2.125:1

These sprocket combinations would be used to return to original rpm/speed ratio:

Stock --- 17 / 34
Heiden - 17 / 40
Hoey --- 17 / 42
Riksoto - 17 / 43

 

[TwoManyXS1Bs]

One more thing to add to the 'advantages' list:

A 'high ratio' primary gearset will make kickstarting easier.

 

[650Skull]

Great info and patience.

Bet you counted that 1 tooth different sprocket twice

 

[TwoManyXS1Bs]

Great info and patience.

Bet you counted that 1 tooth different sprocket twice

Thanx, Skull. Took me most of the day to gather that (numerous net crashes).

I counted that thing 8 times. A little OCD helps here...

 

[riksoto]

I am working with a long time (40+ years) Race motorcycle mechanic/Machinist Craig Hanson in Chico, California 1-530-342-8049. Craig was a competitive racer for years in the US. Craig has worked in the UK and the US for well known race companies.

We have looked at many issues with the XS650. We have identified a few issues that we believe can be remedied.

The reason we looked at the gears was to reduce the stress on the engine cases by swapping the gear ratios between the primaries and the final drive or at least get as close as possible with the space limitations.

We looked at the clutch for three reasons, 1..we wanted a lighter/smaller clutch to reduce the inertia making it easier to shift. 2...we wanted it smaller to keep it out of the oil and by so reducing drag and heat. 3...we wanted common, modern, hi quality components.

We looked at a sump extension to keep the oil out of the flywheels, to reduce drag, reduce temps, reduce oil aeration, reduce oil breakdown, and reduce oil mist in the cases(to keep oil in the cases and out of the vents).

We have looked at long rods to move the power band higher in the RPM range.
Better pistons, that are lighter than stock pistons, lighter thinner modern rings(to help with flutter at top rpm)

We have looked at the heads. Craig offers a porting service for the XS. He machines and welds the exhaust ports then moves them up an in toward the center as well as raising the intake port.

There was a post above asking what was my RPM at 75 MPH. I assumed the person asking the question was on a street bike traveling the highway. I was giving a sprocket ratio that would be the same overall reduction as a stock bike. I must admit that I did not even consider any other option when asked me the question regarding a highway speed.

I meant no disrespect in my previous posts I was sincere when I said you were correct.
The other part of the posts were merely information to consider.
I am sure that your friend tried things throughout his racing career that others said wouldn't work and he found some benefit that he still uses today because he looked at a problem and approached it differently than the leaders in the past. I think that if we don't find new solutions for old problems we still have old problems.

Thank you for you time
V/R
Riksoto