OzVMX Forum
Clubroom => VMX Sidecars => Topic started by: EML on October 19, 2011, 03:22:21 pm
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I'm looking or a DR500/600/700 guru in Brisvagas. Someone that can breath some fire into it and not steal all my pennies.
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I would keep clear of fire breathing the dr500, I have raced one for the last six years
when i got it, it had a broken gear dog
So i did a full gear box rebuild.
last saturday I dumped the oil and the new gear is broken again a broken dog siting in the sump
I have a spare gear box in bits ,and that has the same one broken as well :'(
Its the 4th gear on the sprocket shalf it runs 2nd and third as well, it has three small dogs on each side of the gear.
The other gears have four dogs on each side or 3 larger ones than the weak one above.
Its a shame they go well ,
Im not sure how much it will cost to get a gear made stronger there is room for bigger dogs on it....
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Litres Of fuel and a match should solve all your problems ;)
I take it you have removed the counter weights etc
Pistons Std = 88mm x 20 pin - so you can use XT/TT/SR 500 1mm over = 89mm
but will need to do a bit of work on top of piston as DR 500 are 4 valve.
Honda Xr 500 are 21 Dia pin so are are no good to us.
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which fuel Oldfart-premium unleaded or methanol, and will a bic lighter do the job or some BBQ matches???
I don't recall ever having gearbox issuses back in the day with Geoff Udy but hay, I was just the nut on the side.
There was talk that one guy ran a 700 then too and Walducks Suzuki in Townsville ran some at the speedway that were way quick in midget cars.
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You can work the top end of the DR500 buy the sounds of it ,
With larger pistons..
but will break the gears for sure,
I have three broken ones to prove it and im easy on gear boxes because i dont like rebuilding them.
My two DR500s run stock pistons ,but I run 38mm flat slides and bigger dia header pipes etc etc.
I did think of removing the counter weights but was conviced buy a bike machanic to leave them there .
The counter balance weighed around 3kg to 4kg all the cogs chain etc.
So its a fair bit of weight saving on the heavy girls.
I have TT500s as well there gear dogs are twice the size and I have never broken one in 20 years. 8)
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All the broken gears i Have..
They Have only had only one broken dog missing out of the three on it
so it still works, you cant realy notice it missing when going through the gears .
But its in the back of your head if the others go or not.
I do race starts in 2nd gear what runs of 4th gear what is the weakest link.
So its a bit of a worry
thats my take on it
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thanks mick, it all helps.
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i have removed my balance shafts and it makes them rev quicker.I have never had any problems with my gearbox and i do give the old girl a hard time.I have fitted a dr600 flat slide carby which is a great improvement.The only work i did to head was clean up the ports and match manifolds.Hope that's some help.
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Hey EML. You remember the DR outfit we had. Wiesco piston, Ivan Tighe cam, (they might still have the specs) and the bit that made the bigest difference was installing a Amal carb. Never had a gearbox issue.(http://i1090.photobucket.com/albums/i369/QLD7791/Davesoldsidecar.jpg)
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JEEZ Dave, still looks fast just sittin' there. Ask Max what size it actually was pls.
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I'll ask, but Max didn't build the engine. Try asking jeff as we had exactly the same piston. ;D
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i think gear breakages also depend on riding style. I still hear of people flat shifting ::) XR/XL500/600 & TT/XT600 were all known to break gears with sidecars too. Everyone that one one knew it and was aware of it but it was just part of racing but it was not like a gear broke every event. It was never as big a deal as people made it out to be and everyone just had supplies of spare gears. If you started with a full set of very good gears that was a big help.
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Thanks Leith, as I mentioned earlier, I don't recall Geoff ever having gear issues but I guess they were all new then.
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If you cryo the gears & fit a cush drive rear hub that should stop it, it's how we make the XL350 work as they like to blow the drive dogs off when you are making big hp.
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Interesting thing about the cush drive, I have two rear hubs that came with the wreck I bought and another full wheel assy. They all have different size axles! They are all from DRs of different vintages and the complete wheel is cush and off a DR400 road trail. It has the biggest axle and wont go through my swing arm.??
Either way I'll be building new wheels up by the looks of it in any case.
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my DR500 had a crush rear wheel on it when i got it but had a broken gear in it,(note standard wheel)
I put a rm 250 1984 rear wheel on it to save weight ,not crush drive and broke one again.
I dont do flat shifts ,I dont do push starts because of extra stress on gears etc.
I always use the clutch when changing gears .
IF you have the gears sets laid out like I have you guys will Know what Im talking about.
I am easy on my bikes ,gears etc ,I am fussy and look after them
They are just to small dogs i can send pics of broken ones.
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Mick, has this problem happened with the same engine, every time?
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Hey slide,
its happen twice on one motor,
when i first brought the bike i rode it around the padock all seemed fine with the gears.
i gave it a oil change and found a gear dog in the sump.
So i did a full gear box and top end rebuild and six years later found the broken peice in the sump again broken again :'(
I picked up a spare motor from a wreckers for parts when i first got the bike , for parts not just for gears etc.
and last weekend checked the gears in that one
and that one is broken as well, its the same gear broken as the fist motor.
I have two DR500s but the second bike hasnt been pulled apart to check that one , i raced it a few weeks back it runs fine ...
so one motor has broken two .
and a spare motor i got from a wreckers was broken as well not broken from me.
and the second bike i havent checked yet..
So thats three broken all up, but i have only broken one ..ITs the size of the dogs on forth gear they are smaller than the rest and break
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I def wasn't questioning you Mick, just thinking maybe an isolated problem with that particular engine.
I race one on dirt track withva Cush drive hub and no prob's yet, touch wood.
Watching with interest and I'd love to hear from the sidecar boys what they've done to their race engines.
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We'll be working along on one shortly Slidze.....years ago Geoff Udys only had an Electron Blue carb and a shortened std exhaust and it used to hand it up to all but the biggest of the twins...and you can't say it was power-to-weight, can you. :D
Maxs one pictured above was rumored to be 700cc but we don't have proof yet-I'll check with Serco to see what piston they could use.
Stay tuned over the summer.
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You buggers put the mockers on us-last sunday at Nudgee the other DR500 broke the box-wont kick start-so just as you said.