Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: boze on March 10, 2007, 03:00:52 AM
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hey ppl, i got the old SR500 on the road and everything, ive just got back in from a run and ive noticed something wierd, if i accelerate hard and get to a certain speed i hear a kind of crackling coming from the front of the bike, its very disconcerting and i was wondering if anyone could possibly shed some light on the matter, anyone else had a problem like this? It doesnt appear to affect its performance or anything its just a little worrying.
regards
damo
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pinking/detonation?? Give me a shout if you're through East and I'll have a listen!!
Meantime do a plug chop and see how your mixture is..
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pinking/detonation??
i dont know what pinking is...:( i do think she might be running a bit rich though, she starts from cold no problem at all but if ive been a run then switch her off for a moment she doesnt really want to start till ive left her for a bit to cool down....does that make any sense? how do i adjust the mixture? any help is greatly appreciated :)
damo
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Aye boze,
Pinking is the noise you get from the top end of the motor when you put it under load (accelerate) and the air/petrol mixture explodes or detonates before the piston reaches Top Dead Centre, or before the spark plug sparks and ignites the mixture causing it to burn. This can blow a hole in your piston, burn out the valves so that they no longer seal, break the big end bearing!!!!!!!!!!!!!!!!!!!!!!!!!!
Take your plug out and have a look at the porcelain insulator around the central electrode. Is the spark plug the correct one for the SR500? Does the insulator look black, sooty, wet (Rich)? Light brown/yellow, slight deposit, dry (OK)? White, melted, crisp with bits flaking off (Weak)?
Was the plug loose when you removed it, can you hear air hissing on the inlet side of the carb or cylinder head area (weak mixture)? Exhaust gases leaking from exhaust side of the head (weak mixture)?
Is the original air filter and exhaust still fitted, have either been modified or removed and replaced with alternatives?
Buy a manual (Clymer, Haynes or Yamaha) from Ebay and read it from cover to cover at least three times before laying a spanner on the bike!
Have a browse through this website: http://www.thumperpage.com/articles/sr500faq.html
Have a browse through this website and enjoy the pictures as well: http://www.sr500club.org
Have a browse on this website and go and have a blether with them: http://www.ayrclassicmc.com
Ayr club meet in the Glenburn Miners Club, Glenburn Road, PRESTWICK, every second Wednesday in the month and have a very diverse range of interest and knowledge. The craic is nae bad either!
I hope this helps and that you get sorted. I'm not trying to be a BOF!
Regards, Bill
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Beat me to it ;)
Cheers Bill :D
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To me pinking always sounds like someone smashing glass on the engine.
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thats almost definately what it is, ill sort the air/fuel mixture today, ive got a haynes manual so ill be ok :)
thanks for all the help people!! ill get some pictures of the bike sorted as soon as possible :)
regards
Damo
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Have you done anything that may have altered the timing or the compression?
Ken
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Have you done anything that may have altered the timing or the compression?
Ken
not that im aware of, i did strip and rebuild the carb a few months ago as the fuel pump diaphragm was shot to pieces but i did it in accordance with the manual. everything is completely factory standard, no air filter mods/engine mods/exhaust mods.
Steve H: it does sound like glass smashing on the engine its almost definately pinking.
Bill: Ill check out those links, cheers!
damo
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Fuel pump diaphragm ?. Do you mean the accelerator pump ?, this is a small cylinder/pump which squirts fuel into the intake when the throttle is opened quickly. This could be be the source of your problems. The idea is that when you open the throttle quickly the fuel does not respond as quickly to the new throttle postion as the air does, and it weakens the mixture off. The accelerator pump is supposed to compensate for this sudden mixture weakness with a squirt of fuel. If it isnt working properly this could explain the pinking when you accelerate.
As and aside I first found about accelerator pumps when I looked down the barrel of an XL500RC carb and opened the throttle to check the slide movement, an eye full of petrol is not to be recommended !
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no, its a small flat rubber coated piece of fabric with a flat circular metal piece in the centre, it secures a spring on the other side of it, i am led to believe it creates the vacuum needed to start, or something like that.....but anyway, it was all crumbling away and i managed to order another online to replace it with.
damo
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Dunno if the SR has an accelerator pump but what you're describing certainly could be one... either way I'm sure we'll get to the bottom of it :)
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Accelerator pump - or a vacuum tap diaphragm maybe? - Either way sounds like pinking to me - says he being really useful and adding to the conversation.
R
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Look at this and tell us which bit you changed http://www.siue.edu/~rsutton/SR/mikuni.htm
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Look at this and tell us which bit you changed http://www.siue.edu/~rsutton/SR/mikuni.htm
um you cant see it on that pic, its part number 7 on both pictures on this page http://slash5.net/sr500/b0000dcc.gif
and part number 18 on this diagram (both the same part btw) http://slash5.net/sr500/b0000dcb.gif
damo
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Definately the accelerator pump. You can see the rocker arm which moves the diaphragm is connected to the throttle wheel ?. I this isnt working it would cause a weak mixture when you crack the throttle open. Take the carb off and with a flost full of fuel open the throttle, you should get a jet coming out of the carb throat, DONT look down the throatas you'll get an eye full of petrol.
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how should the rocker arm work? when i open the throttle part number 4 on the left diagram http://slash5.net/sr500/b0000dcc.gif moves down but part number 6 on the same diagram doesnt....could it be the spring is weakened? maybe badly adjusted? i just reckoned that since the pump lever (part 6) isnt moving it wont be squirting any fuel anywhere....
im ordering a gasket set as i seem to have an oil leak around the cylinder/everywhere...when i take the engine out ill whip the carb etc off, im ordering a new air filter too as the one thats on it is slowly falling to pieces...
damo
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Have you checked the exhaust is tight at the header pipe/head joint (might be leaking when under a lot of pressure) check for any sooty lines or marks?
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i left it too long and it broke down on me on the way to work this morning :( i ended up getting frozen and soaked to the bone at 6am at the side of the motorway. ive ordered a new accelerator pump diaphragm which ill be doin as soon as it gets here and also ill be doin the gaskets. im gutted :( theres a few other bits and bobs i need to sort too....
need a new chain and sprocket set (front and rear)
need to change the position of my headlight as it is pointing too high
need to get a small screen as i dont know how much more my neck can take...
gotta scrub the engine as its absolutely filthy...
need to respray the exhaust too as its gotten a little chipped now
general repainting and polishing
needs a new air filter as this ones starting to disintegrate
some bits of rust needing vamoosed :)
anyone else here part of ayr classic motorcycle club? im thinking about joining.
damo
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Aye damo,
Bad craic to breakdown this morning, good to know you managed to get off safe. I don't belong to the Ayr club but have met a few of the members and they seemed a friendly crowd. Turnup for a blether, you don't have to join straight away, surely?
Hope you get the bits and fix things soon, the winds back in the NE and that means the West is best for the weather and looks fair for the weekend.
Cheers, Bill
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nice one bill :)
i had the engine out today, changed the cylinder gaskets etc, didnt have the mental strength to split the engine today due to recent events!! the other gaskets look fine though. upon closer inspection the exhaust gasket was virtually non existant and there was quite a lot of soot deposits around the exhaust manifold and cylinder head etc
the diaphragms were melted to pieces so i got a couple coming on tues or wed to pick up from Ride On in glasgow. Im gonna attack the engine casing tomorrow with a tooth brush and some cream cleaner...
couple of pics:
(http://i85.photobucket.com/albums/k62/saltmason/DSC00552.jpg)
(http://i85.photobucket.com/albums/k62/saltmason/DSC00551.jpg)
will update soon.
cheers
Damo
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Damo
Good on you
Take it slow and take it easy
Will have a nice bike in the end and current poster apart - meaningful info from the peeps on here.
Hope it is running good soon
R
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Aye damo,
That's the beauty of the older SR. Whip the engine out nae bother, ruddy SRX motor is that tight to the frame you need the Khama Sutra to get to the engine and then a truss to remove it!
Go canny, Bill
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right thats the engine cleaned up a bit now and back into the frame.....although i have a bit left over.....looks like some sort of little bracket...ill get a picture up tomorrow but i dont think its really THAT important....
i somehow managed to bugger both my rear indicators so ive ordered a new pair off M&P and also bought a new spark plug, air filter and flasher relay from wemoto after realising the spark plug that was in it was the wrong one!!! DOH!!
ill update soon.....
Damo