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Post by fenz on Apr 19, 2007 6:38:58 GMT -5
I was reading an article the other day about the protec TT 500 race bike that they built for motocross in the early 1980s.
The bike was built with max power in mind and all the development work was done using a dyno to prove their mods.
The bike was close to 600cc and ran 11:1 compression with the final output being a bit over 51 hp with massive tourque figs.
Now what i was wondering is there any owners of modified 500s out there that have had their bikes on the dyno??
There has been 20 odd years of development since the protec bike was built so what sort of output should one expect from a mildly tweeked 500 to a real wild build up.
The new generation yamaha singles (yzf 450) are cranking out close to 50hp in stock trim from memory.
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Post by milkman on Apr 19, 2007 9:19:43 GMT -5
Good question Fenz,
I was contemplating that when reading the VMX article I was put onto and cafercaer.com.au were saying its not that hard to reliably have double the standard output.
Intersted to know if anyone has bothered trying to mod a late model thumper engine into their SR. I dont see the point really, the effort requiredt would be headache to what can be drawn out of the SR lump.
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Post by colinjay on Apr 19, 2007 22:59:32 GMT -5
Hi,
With these new generation YZF 450, they might put out 50 odd HP in STD tune, but they don't have real good engine service lives. A friend of mine is a bike mechanic and told me the service life for a set of rings is sometihing like 15hr! they are basically a full on race tuned engine. Obviously you can run the engines for a lot longer that that, but the performance starts to suffer as they wear out like any engine.
If you get a chance to have a look at the piston out of one of these engine, they are almost flat, and have absolutly no skirts on them.
Even a SR engine putting out 40 odd HP would still have a desent service life, so that is what I will stick with.
CJ
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Post by StewRoss on Apr 20, 2007 3:12:19 GMT -5
Hi, Yes that's true and when the new ones wear out it's pretty expensive...Titanium this and that... I would love to have a CRF450 or a Yam 450 but I reckon that I will resist. My mate has a Honda that he's modified to Supermotard spec so I'll satisfy myself with a ride on that. I am still having plenty of fun playing around with the SRs. SR  |
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Post by frankyb on Apr 20, 2007 16:08:16 GMT -5
Hi guys, we see modern 450 thumpers all the time at dirttrack meetings. Fast they are, but reliable theyre not. They all seem to suffer from a lack of torque as well. A young guy who races with us has a crf450 for the modern classes, but also runs a79 model tt500 in the classics, and he is almost always a second a lap faster on the tt500. My daddy always said that revs sell bikes, but torque wins races, and i reckon he was right. Anyway, the guys on their crusty old classics always have the biggest grins, we know whos having more fun. Cheers Franky b.
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Post by davedunsboro on Apr 20, 2007 18:44:57 GMT -5
Thats quite right anybody can go buy the latest A-Z 450 but you can't just go get a SR,TT or XT can you , thats what increases the grin factor . Espesially seen as some guys have actually owned their bikes from new and could be on their 5th or 6th rebuild/vamp . Cheers Dave .
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Post by wotavidone on Apr 22, 2007 20:02:15 GMT -5
Went down the bike shop for a couple of oil filters on Saturday. $42 bought me enough oil and filters to service both my bikes (XT and SR). Service interval according to the owner's manual is 3000km or 2000 miles. 1 litre of thumper oil and a filter for a WR450 is about $28, but the guys I know who own them are changing the oil every 500km. Shop owner tells me the 450 honda is the same. Bugger that, I'd rather be slower and not spend all my time working on the bike.
Went to a rally at Booborowie on the weekend. Amazing how many people pull up short to surround the SR and discuss the finer points. Bet they'd walk staright past the modern thumpers.
Mick
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