OzVMX Forum
Marque Remarks => Suzuki => Topic started by: SON on December 07, 2012, 10:23:51 pm
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I am about to get 4 cranks rebuilt 2 with standard length long rods
2 with shorter rods
Is there any demand for any more?
Price will be about AUD$425 including new rod kit
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What stroke?
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What would you like?
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I am thinking of doing two different lengths
A little R&D
1 for MX
1 for Flattrack
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Interested in Mx version... cams are problem they tend to wear out the carrier.
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I am about to get 4 cranks rebuilt 2 with standard length long rods
2 with shorter rods
Is there any demand for any more?
Price will be about AUD$425 including new rod kit
What does changing rod length do on a fourstroke??
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Long rod is better for several reasons
However that will require a barrell base spacer, a longer cam chain and a bit of work to get the compression and valve clearances just right.
The squashed or shorter rod Might??? Alleviate the barrell spacer, allow the standard cam chain and is generally easier to set up, big downside steeper angles don't like revs but should be OK for VMX.
My TT 605 runs the Powroll short rod stroker but is for MX
I would not run a short rod stroker on Flattrack.
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Sorry, been without a computer for some days.
I don't know much about these engines, just that I had one as a kid, and would love to build something cool for MX with a DR engine. I don't even have one anymore...
I don't have the knowledge to calculate the compromise between stroke and rod angle, but it would of course be best to have as much cc as possible.
If I where to buy a crank I would like the short rod type, as this engine is tall enough...
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Better question/answer is MX bottom end mild revs V Flattrack top end high revs
Answer your own question but shorter works for me
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SON, what stroke do you reccomend as max with a shortened rod then? For MX.
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Long rod is better for several reasons
However that will require a barrell base spacer, a longer cam chain and a bit of work to get the compression and valve clearances just right.
The squashed or shorter rod Might??? Alleviate the barrell spacer, allow the standard cam chain and is generally easier to set up, big downside steeper angles don't like revs but should be OK for VMX.
My TT 605 runs the Powroll short rod stroker but is for MX
I would not run a short rod stroker on Flattrack.
When you say shorter rod, do you mean standard length rod ?
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When you stroke a crank you off course need to shorten the rod by half of the total increased stroke, to keep the piston stopping at the same height. This comes at the expense of a less ideal rod angle.
When you stroke the crank and keep the original rod you need a spacer of half of the increased stoke at the bottom of the cylinder.
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Somewhere in the "files" there is considerable discussion on con rod length and the associated variation in rod angulation (is that a word?)
I found it very interesting in light of my experience in the '60s were short rods were the "in thing".
The summary in my head indicates that shorter rod equals more torque at some limited rev range, all the current experts seem to agree that longer rod is better overall.
(still talking engine!) ;)
pancho
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Longer rod = heavier rod so there is a significant trade-off
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Long rod is fine for flattrack where you want the flywheel weight,
I have photos of the DR engine with the Yamaha rod, I just don't know how to post them,
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I have disassembled the SP370 with the TT500 Crank installed,
it has been narrowed slightly and several mm turned off the diameter
looks like the Suzuki flywheel goes onto the Yamaha taper but will measure tomorrow
Have photos just have to learn to post from my apple
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Longer rod = heavier rod so there is a significant trade-off
You can almost always remove material of the crankhalves around the pin to compensate.
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I have disassembled the SP370 with the TT500 Crank installed,
it has been narrowed slightly and several mm turned off the diameter
looks like the Suzuki flywheel goes onto the Yamaha taper but will measure tomorrow
Have photos just have to learn to post from my apple
Looking forward to it, how big is the spacer used?
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Have photos just have to learn to post from my apple
You need to upload them to Photobucket.
You can do this as per Roger's guide (link below)
It has changed a bit since this guide was made but if you choose classic style then it should make more sense
http://ozvmx.com/community/index.php?topic=17785.0
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I know the 370 and 400 look similar but as I understand it the 400 is beefed up. I'm not sure what is the same and what is not.
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I will know in a few hours I have a 370 apart on the bench and a 400 engine out of the frame ready to come apart.
the 370 is engine number SP370-100065
I will be at work in 3 hours so I will post then.
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Looking at the Clymer manual there is mention of a 450 Powroll stroke kit . The picture seems to show a standard rod. Anyone know how a DR piston compares with a XT piston?
I know in standard form they are not interchangeable [disregarding the bore size] as if they were someone would have done it after 30 years, but I would guess that possibly the pin OD might be the same [DR 20mm]. If that is so what is the distance from top of pin to top of piston for a XT piston?
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If it's any consolation, both SP370 and XT500 pistons are/were used in XS650 hop-ups for sidecar cross.
Wally Wasp might know more.
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XT TT SR 500 (87mm) 20mm pin 1mm over = std bore 88mm on the Dr 400 10: 1 comp
Or go with the 90mm pistons with 11.1 comp or 12.1 comp. Piston will need to be modified some what.
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To get a 450 the stroke has to be 74 which is 9 up the DR's 65.2 so I guess the XT taking 2mm of half that still leaves approx 2.4 mm for extra compression. I've bent a valve with the standard set up, and that still leaves valve cutaway and piston skirt as unknowns