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Post by wizz954 on Mar 22, 2006 21:24:16 GMT -5
Hi All, I'm a newbie and bought a 78 SR500 a month ago and optimistically prepared it to race at the Barry Sheene Memorial race meeting at Eastern Creek. All seemed to go well initially barring jetting and air filter setup. That was mostly sorted over the weekend but the biggest problem I had all weekend was overheating. It got really hot on Saturday and had to limp it home after only 2 laps so I fitted an oil temp gauge on Sunday and after 3 laps it was reading 130 deg C when the bike basically cried enough and stopped  . Before this happened it was running well and got around in 1:02:98 on lap 2 which I have been told is good for a stock motor  I have the underlying problem to fix which is going to be interesting  , but everyone tells me it needs an oil cooler whatever the problem turns out to be. Has anyone out there fitted an oil cooler and if so, what oil cooler and is there a simple way to mount one without welding? |
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Post by hopwheels on Mar 22, 2006 23:51:50 GMT -5
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Post by wizz954 on Mar 25, 2006 6:49:46 GMT -5
Thanks Gary, I've seen the oil cooler before and thought it looks great but need a German translator to work out the description! The mod to add an extra oil line to the exhaust valve has already been done by the previous owner (added rigid pipe similar to stock oil pipe). Need to know the id of the oil line kit to see if it will increase flow or not. I think std pipe is 3mm? Picture of bike at Eastern Creek - March 11 2006. Still work in progress having only had 3 weeks to get it to this stage!  |
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Post by hopwheels on Mar 25, 2006 10:47:59 GMT -5
That looks ready to rip! Very cool. That ebay seller (biebo) speaks English I believe, and will answer emails in English. Not sure of the ID on the two-line oil line kit (mine's already installed), but the OD is 10mm.
Gary
Hopwheels
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Post by wizz954 on Mar 25, 2006 19:57:30 GMT -5
Yeah, it looks great compared to what it did a few weeks ago!  I had a good look at Biebo's eBay store and asked him some questions. I found a carbie heat shield that is supposed to keep the float bowl cool, theory is heart causes air bubbles to form and cause fuel starvation, lean running and overheating. This could be a contributing cause of my overheating, seems there are many potential causes. |
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Post by StewRoss on Mar 28, 2006 3:58:10 GMT -5
Hi. Nice 500. I like the pipe...loud? Where did you get the muffler?
Interesting about the overheating. What type of oil temp gauge did you fit? Is it the one in the filler cap?
I have that type fitted to one of mine and have not seen over 90 degrees on it, admittedly in road riding, but that was on a pretty hot day.
I have ridden my SR's fairly hard over the years, and never experienced anything similar...
What have you done to the bike as far as tuning is concerned? Is your timing correct, that and perhaps lean running I'd be checking initially. Low oil level....?
Was the oil filter OK? Around the right way and the bypass working OK? (Not sure what effect that would have regarding temp...) Spark plug the right heat range? For racing at least an 8 or a 9...
Perhaps consider a Mikuni VM series carby. 38mm? Simpler in the long run...
Certainly you'd get a nice cooler from Japan through Deus...I'm going to machine up a finned alloy cylinder mounted to the front down tube, to use on my new cafe racer...when I reach that point. I have a Lockhart cooler that was meant for a HD, that is available from HD shops...I can't recall where I got mine at the moment. $200 and something dollars...
Oil lines...I have several types. On one bike I have the old standard original one and the later model chrome SR type fitted together.
On the others I have varying types of flexible line to the exhaust rocker. None have caused me any difficulties.
Good to see another SR on the track.
Let us know how you get on...
SR
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Post by wizz954 on Jul 1, 2006 4:52:06 GMT -5
SR, sorry for the long silence, had lots of things to sort out with the bike and the truth can all be revealed.
In answer to your previous questions:
The muffler is a Conti muffler that I bought from a mate and it is loud!
Timing was spot on and mixture was right, running a 370 main jet with K&N pod filter. Oil level
high side, new filter too. NGK BP8ES plug, slightly harder than standard.
The oil temp gauge is Daytona and fits in the filler cap. Since having a top end rebuild I just got the bike on the track to run it in. Just revving up to 6500rpm, the temp is around 80 degrees, rising to around 90 degrees when taking to 7000rpm. That's a lot better so now the 64 million dollar question, why did it overheat in the first place?
The bike was standard or so I thought. On doing a compression test, we found it had only 80psi and this went to 120psi with some oil down the cylinder. This suggested knackered rings, so we stripped it down and found a bit of a mess. The top ring was the only one doing anything, the other 2 rings were stuck in the grooves. The piston was also melted, the centre of the piston was concave! We also worked out it was a 11:1 comp ratio piston.
Now it is running exactly the same carbie settings as before except the needle raised from 3rd (middle pos) to 5th position (richest), so fuelling was close to right. So my 2 theories are:
1) 11:1 comp piston was not getting enough octane (Shell Optimax 98) causing it to detonate
2) Blow by from stuck rings was causing combustion heat to transfer into engine and subsequently causing meltdown
It might remain one of life's great mysteries, but I'm happy it's now running OK and looking forward to finishing some races!
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Post by wizz954 on Jul 1, 2006 4:54:51 GMT -5
Forgot to add..
Now running Wiseco 10:1 comp piston 88.5mm
Stainless one piece exhaust valve
Re-profiled cam, slightly lumpier
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Post by StewRoss on Jul 2, 2006 3:48:05 GMT -5
Hi,
The piston crown damage that you describe is typical of severe detonation. That can be due to an inefficient combustion chamber/piston crown shape, hot plugs or the use of lower octane fuel in a 'high-comp' engine.
My experience with high-comp pistons in the SR has been that unless you use the higher octane fuels then you risk detonation. I fixed this in one of mine by using 100/130 AVGAS...a simple enough solution. That bike's piston would rattle badly under load on acceleration etc. AVGAS instantly fixed the problem; also gave the engine an instant torque increase all over.
Other's I know have reshaped the piston crown and the head combustion area to reduce the problem. They can often use lower octane fuels OK.
For racing, AVGAS would seem the easy solution...
SR
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Post by StewRoss on Jul 2, 2006 3:56:24 GMT -5
Oh yes,one other thing, that 88.5mm Wiseco piston is supposed to be of a better crown shape that reduces the possibility of detonation. Let me know how you get on with it.
I have one of those sitting around here that I am going to fit to a bike I am currently building.
SR's seem to be louder that other similar capacity engines. Cam timing or something...So pipes that are acceptable on other big singles like Conti's for Ducati's etc. are often pretty loud on the SR. I have one SR roadbike with a Staintune Conti replica on it. I will leave it there because it looks great, but it is loud. Cars know you're around though...
SR
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Post by wizz954 on Aug 3, 2006 8:15:56 GMT -5
We have one new development, another possible contributing factor to lean running. The inlet manifold is so perished inside that the lip that locates the carbie in the manifold disintegrated and was allowing air to be sucked in while on the dyno today. We discovered it because the air/fuel mixture was all over the place and we couldn't figure out why.
One new inlet manifold now on order.... good news is we saw 40hp before the carbie shot out of the manifold!
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Post by wizz954 on Aug 8, 2006 4:07:59 GMT -5
The engine ran fine on the track but ran out of breath up top. I'm still thinking there is a leak in the manifold or a poor fit. The large K&N filter seems to put a lot of weight on the back of the carbie and it droops. There was also a noise that I cannot distinguish between camchain noise and pinging. Only seems to do it along the main straight when running up through the gears at full throttle, but still rattles when I back off slightly but still under load.
Managed a 2:00:9 lap so we're starting to look competitive. Only another 5 seconds a lap required to match the class record set in March!
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Post by fe2cruz on Jun 24, 2007 21:49:19 GMT -5
I'm not racing but I was wondering
with added weight would I need
an oil cooler too?
I have a 78 SR500
custom opened pipe
90mm piston
Mikuni VM36
K&N cone & breather
oil line mod (rubber)
small sidecar
mounted to the frame
I haven't taken it on a long
hwy trip yet as I am still
adjusting the mounts to cope
with the frame vibrations.
But I did do a short 5 mile run
holding 78 mph on my speedo on
a mild afternoon/evening and
the engine didn't feel hot at all.
With the modifications and the
extra weight would the SR500
start to get tired after a hot
day on the hwy?
What oil coolers would be best?
-christiaan
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chuck
New Member
Posts: 11
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Post by chuck on Jun 24, 2007 22:28:11 GMT -5
Hi to all, and in reply to Christiaan, I find when I go up the Hume Highway to the annual SR rally(go that way so my partner in campervan doesn;t get lost, would much prefer the twisties) that the temp starts climbing over 110 deg after a while. Ive bought a Honda XR400 (horsehoe cooler) which you get on Ebay now and again. Need to make up brackets. Also because I live in Tassie(don't know how the guys in ACT go) if I ran with the cooler in winter the oil would never warm up, so I got a Lockhart thermostat( doesn't divert oil to cooler until temp over 80 deg).
biebo in Germany sometimes sells a Mocal thermostat one which is a bit dearer. His cooler probably works well but it looks too big stuck down off the side of the downframe. A bit Harleyish and not the caferacer look.
Hope this helps
Charlie
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Post by wizz954 on Jun 25, 2007 7:00:38 GMT -5
I think Biebo also sells an oil cooler that looks nice and has fittings so easy to mount.
I would say a sidecar with passenger would load it up a bit and an oil cooler would be a good precaution. Depends on the climate/temperature as well. If you live in a cold place, it's not such a problem!
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, but everyone tells me it needs an oil cooler whatever the problem turns out to be.
