Dakar Dazed II - the return! Part 1: Project LC4-50

[JMo (& piglet)]

Originally Posted by Brodovitch

edit: Looks like we will have a common RB holder fitted as well

Hee hee - really? - it must be magnetism drawing us together...

Very much looking forward to the Hellas for sure - see you there!

Jx

[640 Armageddon]

Originally Posted by JMo (& piglet)

Hee hee - really? - it must be magnetism drawing us together...

Very much looking forward to the Hellas for sure - see you there!

Jx

[Brodovitch]

Originally Posted by JMo (& piglet)

Hee hee - really? - it must be magnetism drawing us together...

Very much looking forward to the Hellas for sure - see you there!

Jx

[JMo (& piglet)]

Originally Posted by neduro

Great idea and look forward to seeing the execution.

The 450RR has proven itself to be amazingly reliable for what amounts to an uprated motocross engine, but to me, something died with the 450 formula. The days of the Malles Moto rider taking care of the same bike for long periods isn't the same in the new era... which is where your project comes in.

Will you use any of the good bits off a 690 RR (longer swingarm, etc)?

Hi Ned! - Yes, we were all set to debunk the 450RR this year after Dakar, only for loads of them to finish on a single engine (doh!) - although I think a lot of that was risk-tactics, especially at the top end of the field with the racing so close this year?

It certainly seems the Factory have got their act together regarding longevity from the 450RR engine now - although I still think it is a brave soul who would enter a bike like that without taking at least one spare engine 'just incase', which makes an extremely expensive bike even more expensive!

Taking a spare engine also means you are not eligible for Marathon class - which as you point out, and I'm sure many would agree, is very much the privateer spirit and the original ethos of the Dakar as a long-distance endurance event - where traditionally you stand or fall not just on your speed and/or navigation prowess, but on the very fact you can get your vehicle to the end of the rally without breaking it...

As I say, we are not setting out to prove we can engineer a front-running race bike, rather provide an excellent (in our opinion) platform for the clubman level rider who wants to race a whole season [or a Dakar] on the same engine, with low maintenance - essentially, as you suggest, something that would be an ideal Malle Moto machine - which in turn makes even the Dakar look a lot more affordable to enter?

Jx

ps. Final chassis spec is still to be decided, but John & Martin have a lot of experience setting up the 690 for rally racing, and I imagine they would prefer to keep as much of the bike as stock as possible (if only to retain the 'budget' ethos of building it around the 690E/R).

That said, as John alludes to above - we will be race-testing one of these new TracTive shocks on the Tuareg this year, with a view to incorporating it into the Dakar bike spec for April onwards... There is another version which is still in the development stage at the moment, and I'm sure John will be along with more info when they are in a position to release the final spec, but suffice to say, it has a very innovative damping set-up, which could revolutionize dirt-bike suspension!

[JMo (& piglet)]

Originally Posted by Desert Matt

Jenny, this is a great concept, and if it proves itself reliable, could see huge numbers on the start podium in future years. Good luck. I wish you all all the best in the project. If you bring the road show down under to the safari, I'll be watching closely.

Hi Matt! - thank you for the vote of confidence!

To be honest, the 450cc conversion is not really designed to be a commercial venture as such - I'm sure Rally Raid will sell a lot more 690 hi-comp pistons they they ever will 450cc conversion kits!

However, as I mention in reply to Ned's comments above, what the 450cc kit does now offer is a serious option for those riders who would like to enter Malle Moto in Dakar (or any other 450cc event) without the almost universal requirement to take a spare engine with you, or to even have to change the oil more than once or twice in an event!

Jx

[KASUYAHO]

It will be interesting to see what way they decide to go with the engine to get 450cc seeing there keeping to same size bore.

Great to see guys / girls thinking outside of the box

Good luck Jenny

[dentvet]

Originally Posted by KASUYAHO

It will be interesting to see what way they decide to go with the engine to get 450cc seeing there keeping to same size bore.

Great to see guys / girls thinking outside of the box

Good luck Jenny

102x84.5 is 690 specs

so 102 bore with 55 mm stroke is 450 cc

so they will lengthen the rod and drop the wrist pin to make up 30 mm in stroke. It sounds like they are doing mostly rod lengthening because they are going to use the same basic piston as a hi comp 690 piston (close to stock wrist pin location therefore)

This should keep the scrutineers scratching their scalps

[KASUYAHO]

Originally Posted by dentvet

102x84.5 is 690 specs

so 102 bore with 55 mm stroke is 450 cc

so they will lengthen the rod and drop the wrist pin to make up 30 mm in stroke. It sounds like they are doing mostly rod lengthening because they are going to use the same basic piston as a hi comp 690 piston (close to stock wrist pin location therefore)

This should keep the scrutineers scratching their scalps

Yer that is one way of doing it.

As i said it will be interesting.

Scrutineers should have a capacity checker.

[barrier]

Originally Posted by dentvet

102x84.5 is 690 specs

so 102 bore with 55 mm stroke is 450 cc

so they will lengthen the rod and drop the wrist pin to make up 30 mm in stroke. It sounds like they are doing mostly rod lengthening because they are going to use the same basic piston as a hi comp 690 piston (close to stock wrist pin location therefore)

This should keep the scrutineers scratching their scalps

Surely they could sleeve it a little without being too small for the valve layout.
But hey what do we know!

[greglewis]

Originally Posted by dentvet

102x84.5 is 690 specs

so 102 bore with 55 mm stroke is 450 cc

so they will lengthen the rod and drop the wrist pin to make up 30 mm in stroke. It sounds like they are doing mostly rod lengthening because they are going to use the same basic piston as a hi comp 690 piston (close to stock wrist pin location therefore)

This should keep the scrutineers scratching their scalps

To me, this is where it's getting very interesting for an armchair engineer/noob like me. It's been established that the bore will remain the same (no cylinder change). I think it also means no change to cylinder barrel length, and the piston top comes to the top of the cylinder at the top of the stroke - it sounds like the stroke is the only variable factor.

Can someone:
1) correct me if I'm wrong
2) explain the considerations between changing the connecting rod length and/or changing the length between the crank pin and the centerline of the crank.

Thanks

Greg

[neduro]

Originally Posted by JMo (& piglet)

Taking a spare engine also means you are not eligible for Marathon class

I don't think this machine would be eligible for Marathon in any event- looking at an older rulebook but:

Originally Posted by ASO

Machines in the Marathon group must be standard, a s delivered by the manufacturer. Machines must conform in all ways to the commercial catalogue issued by the constructor and be freely available for sale. The original repair manual (as used by dealers – no photocopies accepted), as well as all homologation papers, must be presented at the same time as the machine during scrutineering.

When I studied the book in depth, Marathon has become largely irrelevant to anything but the KTM 450RR- you're not allowed to change anything from standard (down to handlebars), meaning there's only one machine that is capable box stock.

I think they've made the category largely irrelevant, but what do I know.

Long rod motors are cool. The longer rod means a longer dwell time, which can really change (and increase) power characteristics. With that said, that's a pretty darn oversquare motor!

One last thought- the Dakar has become increasingly technical in years past, and I think that trend will continue. Do you think the LC4 based machine (with higher weight than a comparable converted enduro bike) will be a disadvantage in that light?

[ktmmitch]

Originally Posted by greglewis

To me, this is where it's getting very interesting for an armchair engineer/noob like me. It's been established that the bore will remain the same (no cylinder change). I think it also means no change to cylinder barrel length, and the piston top comes to the top of the cylinder at the top of the stroke - it sounds like the stroke is the only variable factor.

Can someone:
1) correct me if I'm wrong
2) explain the considerations between changing the connecting rod length and/or changing the length between the crank pin and the centerline of the crank.

Thanks

Greg

Our initial donor engine is an 08 motor,so 654cc.This is 102mm bore x 80mm stroke.
Our initial attempt is to keep the std bore,and gudgeon(wrist) pin height,then move the crankpin 12,5mm nearer to centre of crank,giving the 25mm reduction in stroke needed to achieve 102 x 55= 450cc
But,because of the reduction of swept volume,we have to "lose"approximately 20cc from the head volume to maintain the same compression.That will be the difficult bit,as we will be running the rally cam,so there will have to be quite a pronounced dome on the piston to up the compression,but still miss the valves.

Onward & upwards..........

[greglewis]

Originally Posted by ktmmitch

Our initial donor engine is an 08 motor,so 654cc.This is 102mm bore x 80mm stroke.
Our initial attempt is to keep the std bore,and gudgeon(wrist) pin height,then move the crankpin 12,5mm nearer to centre of crank,giving the 25mm reduction in stroke needed to achieve 102 x 55= 450cc
But,because of the reduction of swept volume,we have to "lose"approximately 20cc from the head volume to maintain the same compression.That will be the difficult bit,as we will be running the rally cam,so there will have to be quite a pronounced dome on the piston to up the compression,but still miss the valves.

Onward & upwards..........

Thanks - I couldn't ask for a more informed response. Please keep posting the progress of the build, and the best of luck!

Greg

[doyle]

Originally Posted by neduro

One last thought- the Dakar has become increasingly technical in years past, and I think that trend will continue. Do you think the LC4 based machine (with higher weight than a comparable converted enduro bike) will be a disadvantage in that light?

I was thinking the same thing. Malles Moto shrinks every year and it seems to be widely accepted (perhaps even encouraged) that engine changes are not too much of a big deal, time penalties notwithstanding.

With shorter, more technical stages and shorter intervals between fuel stops, it would seem the advantages of doing the rally on a single engine are becoming negligible. Of course there are the factors of getting the engine to SA assuming not everyone has the charm of Manuel Lucchese to be able to sweet talk the airline desk to consider it a musical instrument, but getting it there, having a truck transport it from bivouac to bivouac, add in the tools to change it, etc... there are advantages to running a single motor, but logistics aside, the advantages just aren't as great as they used to be.

With the cost of Dakar nowadays, the cost of a second motor and a spot on a truck the bring it along are relatively minor in the grand scheme.

I do really like where this is going though, I am just not sure that the ASO is heading in a direction that is compatible with the true privateers/amateurs any longer.

[barrier]

This is what I love about this place!!!!
We've got JMo going down the bulletproof 450 route, if a little heavy! (Possibly!) (Discuss?)
And then you've got these two threads!
The 'carry a couple of pistons in your pocket' threads!
Great!


http://advrider.com/forums/showthread.php?t=538827

http://advrider.com/forums/showthread.php?t=858840