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Post by grambo on Jul 8, 2006 13:35:41 GMT -5
Here's the deal, I own a 1981 SR500. The engine makes some back pinging noises in the top end so I am going to re-build the whole thing. I have a stock 32mm carb but will have a 38mm carb soon. I am somewhat familiar with rebuilding engines but not this one.
Heres my question for everyone. How big should I bore out the cylinder? I've heard 540 is good. I also need to know what I need exactly to rebuild this engine. Where do I get the parts, what do I use, what do I need,...etc? Anyone with knowledge on this subject please respond. Do I need a new cam, what size piston, what brands to use, etc? The top end needs a rebuild as well. Should I rebuild the tranny?
Post all your advice and opinions please, because I am new to this. Thanks guys.
~grambo~
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Post by hopwheels on Jul 11, 2006 2:05:20 GMT -5
Welcome aboard Grambo. I think you'll get a lot of different responses, and a lot depends on how much money and time you're willing to put into the motor. I can tell you what I've done, but can't attest to its performance yet, 'cause I'm chasing some electrical issues. Mikuni VM38 38mm Roundslide Carb (from Sudco.com) WebCam Race Cam JE Pistons 540cc piston RD Valve Springs White Bros 1 3/4" Head Pipe I've heard good things about Megacycle cams also, and have one for my next motor. If you go to a 540, I've also heard a copper head gasket is the way to go. I found a bunch of parts/gasket and seal sets on eBay. Make sure and check the Eurpoean and Australian eBay auctions. In the states, SR's are flattrack'd a lot, so checking flat track race sites for parts has worked for me also. Here are some of the links. www.webcamshafts.com/www.powroll.com/P_YAMAHA_TTXTSR500.htm (stroker cranks) www.sudco.com/www.thumperstuff.com/Good luck. Post progress and pics! And again welcome aboard! Gary Hopwheels |
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Post by sjef on Jul 11, 2006 11:59:26 GMT -5
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RD
Full Member
Posts: 176
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Post by RD on Jul 12, 2006 18:16:46 GMT -5
Hi Grambo
If you are looking for a copper head gasket try searching this guy on ebay, coppergasket63. he makes a really good product to whatever size and thickness you require for a really good price. I think I paid about $30 Australian each.
Cheers
Rich
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Post by StewRoss on Jul 13, 2006 4:12:28 GMT -5
Rd,
Not sure if it is exactly the same guy, but CopperGaskets are in Adelaide, S.Aus. Good people to deal with.
His contact number is (08) 8284 5994. He makes good gaskets, in a variety of materials...including of course copper. Hence the name I guess...heh, heh...
I have had several head gaskets made by him for my Honda CYB350 racer, difficult to get these anywehere else. They're made of a material called 'graphoid', the same material as the currently available genuine Honda standard gaskets...
SR
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Post by yamatopdog on Jul 13, 2006 19:38:28 GMT -5
rd, my personal opinion, unless some weeping at the head gasket is ok, go w/ a composit gskt such as stew mentioned.a copper gskt would probably give you a slightly higher cr, but in my experiance do not seal the oil quite as well.Bob
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RD
Full Member
Posts: 176
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Post by RD on Jul 13, 2006 22:58:34 GMT -5
Stew
The guy I am talking about is in Arizona.
Cheers
Rich
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Post by StewRoss on Jul 14, 2006 3:47:59 GMT -5
Ah, OK...the guy in Adelaide charges more than $30 as well...
I like the graphoid gaskets as well, they seal the head nicely. Just don't do what I first did though.
I had them copy a genuine Honda RSC gasket that had crush rings around each oil gallery. That caused me no end of oil leak problems from the head. When they re-made it with only the fire rings around the cylinders there were no more leaks. They are really good gaskets.
Different thickness's of copper gasket can allow you to vary your compression ratio a little though...although I've never actually done this myself...
SR
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Post by wotavidone on Jul 17, 2006 17:45:28 GMT -5
Gents,
I am extremely interested in these copper head gaskets. Not least because Adelaide is only about 2.5 hrs down the road.
I got my calculator out last night and after much tussling with Pi times r squared, and massaging the old brain wondering how many cubic millimetres in a cubic centimetre, I concluded that, assuming the combustion chamber is standard at 62.4 cc, or is that 64.2?, whatever, by adding 1.1mm to the standard 1mm head gasket thickness, a bike running a 10:1 piston will have a compression ratio of approximately 9:1. That is, 1 mm of extra thickness adds an extra 5.9 cc of unswept volume.
This might cure my pinging problem. Maybe even go back to 95 octane fuel.
Therefore, a very important question.
Can you get the head off and back on an SR500 without taking the engine out of the frame?
One other - when you put the head copver back on, the bit that goes over the camshaft and carries the rockers, my manual says coat the mounting surface with some sort of Yamaha sealant. What have you guys used? Would love to be able to use some common automotive sealant like Permatex silicon gasket goo or something.
Regards,
Mick
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Post by yamatopdog on Jul 17, 2006 20:28:21 GMT -5
Mick, there is no way to remove the head without removing the engine.as for the cam cover i used a three bond product(i forget the #),you could probably get away w/ a common rtv silicon but dont forget that you will need to remove the engine again if she should leak!Bob
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Post by tradrockrat on Jul 21, 2006 0:20:45 GMT -5
I got my head off by unbolting the whole engine and tilting it to the right side of the frame. Why would I do this, you ask? Cause at the time I didn't have a garage and the wife didn't want the engine sitting on her dining room table.  |
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Post by StewRoss on Jul 21, 2006 3:34:33 GMT -5
Hi,
Three-bond is the go...can't remember the grade, but I can find out easily enough tomorrow. Just tried to ring my mate but he's out.
I use the grey 'Yamaha Bond' but it costs a fair bit and I'm not sure if you can still get it (probably can...). The stuff lasts forever so long as you keep the cap on.
Unfortunately nearly everything that has to be done to the SR engine needs to be done with it out of the frame. A necessary pain I'm afraid...
My DCM however is designed to allow the head and barrel to be removed with the engine in-situ...makes life very easy...
SR
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Post by sr5ooed on Jul 21, 2006 7:10:59 GMT -5
Three Bond 1104. Put on light coat, one tube lasts for ever. Make sure surfaces are clean, flat, and free of nicks.
Ed
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Post by grambo on Aug 7, 2006 15:37:49 GMT -5
I think I am going to just upgrade the motor instead. I think i will keep it stock but just get a performance piston and cam. Which ones should I buy and where?
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