OzVMX Forum
Clubroom => Tech Talk => Topic started by: micko on March 21, 2016, 07:43:46 pm
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Does anyone know the volume (cc) of a standard head or a recommendation for a 76 RM370, thanks in advance
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Cant help you with the cc volume in the chamber, I think you need to adjust the squish first then measure the cc's with a burette or even with a syringe, then calc the effective comp ratio, if you need to read up on this stuff then get the book:
A Graham Bell Two Stroke performance tuning
it helped me a lot.
I think most peolple who are really fair dink about building a fast old two stroke reshape the chamber, over my head though.
Brett
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Getting it welded up and reshaped etc, just wanted to know the original volume as this one has been played with (butchered) before. Cheers
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Are you going to keep the old suzuki shape or going to shape it more modernish? I did one head for rm 125T folowing this man's blog http://www.southbayriders.com/forums/threads/116608/page-5. Head works well but I have not noticed any power increase. I only ride bikes for fun. Was just experimenting a bit. It may work beter for open class motors since they are harder to jet and they also ping a bit I have heard.
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Going for the modern shape and centre spark plug Tomas, hopefully get rid of the dreaded ping !!!
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Just something to consider.
I received a bulletin from MA saying the government is going to phase out the use of leaded fuel of any type for racing. That means it will be come impossible to get avgas etc.
I know that part of making two strokes work with unleaded was reshaping the heads.
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Just something to consider.
I received a bulletin from MA saying the government is going to phase out the use of leaded fuel of any type for racing. That means it will be come impossible to get avgas etc.
I know that part of making two strokes work with unleaded was reshaping the heads.
Kevin. What is MA's view on oxygenated race fuels. There are several brands out there make make good HP improvments.
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Going for the modern shape and centre spark plug Tomas, hopefully get rid of the dreaded ping !!!
How badly is your bike pinging?
My 370 has a 400 barrel with the 370 head. I set the squish at about 050" and enlarged the combustion chamber slightly more than pro rata to maintain or drop the CR. I run it quite rich and have never heard more than a tiny, momentary ping running in deep sand on a hot day.
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The spark plugs were on an angle for a reason. The single down tube frames would block air flow to the central plug so they tilted them out the left so they stick out past the frame and recieve more/better cooling.
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But all the DG heads etc had the plugs straight up and down and in the centre Leith. What about the heads that had the combustion chamber more to the intake side to stop pinging and to run a higher compression. They tried all sorts of things.
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Just something to consider.
I received a bulletin from MA saying the government is going to phase out the use of leaded fuel of any type for racing. That means it will be come impossible to get avgas etc.
I know that part of making two strokes work with unleaded was reshaping the heads.
There will never be a phase out avgas for piston engine aircraft. So we will always have leaded race fuel if you want it. Unless expensive and extensive testing starts for lead how will that ever be policed?
Reshaping the head for unleaded in a myth, the head will work the same with leaded and unleaded. The fuels require different carburetor and ignition settings.
Does anyone know the volume (cc) of a standard head or a recommendation for a 76 RM370, thanks in advance
About 12:1 is the highest comp your going to get away with on a air cooled engine before the diminishing returns set in.
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The spark plugs were on an angle for a reason. The single down tube frames would block air flow to the central plug so they tilted them out the left so they stick out past the frame and recieve more/better cooling.
l reckon the plugs were on an ange so they could be easily accessed with the chamber in nice and tight.
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Just something to consider.
I received a bulletin from MA saying the government is going to phase out the use of leaded fuel of any type for racing. That means it will be come impossible to get avgas etc.
I know that part of making two strokes work with unleaded was reshaping the heads.
Kevin. What is MA's view on oxygenated race fuels. There are several brands out there make make good HP improvments.
The MA homologated fuels are on this page =homologation]http://www.ma.org.au/index.php?id=1984&no_cache=1&sword_list[]=homologation (http://www.ma.org.au/index.php?id=1984&no_cache=1&sword_list[)
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Just something to consider.
I received a bulletin from MA saying the government is going to phase out the use of leaded fuel of any type for racing. That means it will be come impossible to get avgas etc.
I know that part of making two strokes work with unleaded was reshaping the heads.
Kevin. What is MA's view on oxygenated race fuels. There are several brands out there make make good HP improvments.
The MA homologated fuels are on this page =homologation]http://www.ma.org.au/index.php?id=1984&no_cache=1&sword_list[]=homologation (http://www.ma.org.au/index.php?id=1984&no_cache=1&sword_list[)
I had a look and only 3 homologated fuels. One being VP Roo 100 but there are a stack of other VP products that aren't. Is MA or MQ doing any fuel testing at meatings or is it a free for all?
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That joint is out of control with their compliance, political correctness, racial equality, land rights for gay whales etc. Why stick their nose in on that subject when they are flat out administrating their gradually-disintegrating sport ? Who is going to do a fuel test on a 30-bike club day miles out in the sticks ? Idiots.
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I actually hear the new board/director is turning things around??? Maybe a bit of support for them will help us in the long run?
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Going for the modern shape and centre spark plug Tomas, hopefully get rid of the dreaded ping !!!
How badly is your bike pinging?
My 370 has a 400 barrel with the 370 head. I set the squish at about 050" and enlarged the combustion chamber slightly more than pro rata to maintain or drop the CR. I run it quite rich and have never heard more than a tiny, momentary ping running in deep sand on a hot day.
Pings like a bitch Momus, always has under hard acceleration. Rideable but shits me - been a problem forever, tried all that ! Long story, problem is no one over here will attempt to weld up old contaminated alloy, plenty places will machine it etc - so I have sent it to the east coast for the modern treatment, let you know how it goes :)
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l reckon the plugs were on an ange so they could be easily accessed with the chamber in nice and tight.
Yeah that reason too but i have also seen a suzuki service bulletin on changes from A and B models where they said they angled the plug so it could get more air flow.
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FWIW the old TS series had two plug locations. both angled but one was closer to centre and more upright. Ive never had a convincing reason why they had both.(cooler plug or oiled plug or just a spare or even a decom) What i have noted is that the engine ran better,cooler and less pinging with the centre plug. The reasoning i feel is because of the scavenging process of this type of engine. With the flame centralised within the squish band this promotes even burning and lets the squish do its its thing rather than creating hot spots on one side of the CC. I dont see too many plugs angled on modern 2T engines.
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You'll probably find the reason that there are only a few homologated fuels is because the supplier has to pay MA for the privilege.....so they can spend it mostly on Road Racing events.
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Where is the like button Wasp? i have a V50 mark I Moto Guzzi in the garage with conti's and that little bike is an instant trip to Italy sipping espresso in a hillside cafe with a Mona Lisa smile. Bureaucracy kills so many of lifes actual pleasures. Not so sure you could get club reg on a 370 that easy though.
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Standard RM head
(http://i1382.photobucket.com/albums/ah265/michaelandrew64/image_zpsie4adum9.png) (http://s1382.photobucket.com/user/michaelandrew64/media/image_zpsie4adum9.png.html)
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You'll probably find the reason that there are only a few homologated fuels is because the supplier has to pay MA for the privilege.....so they can spend it mostly on Road Racing events.
::) that would be wrong......
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Re Pinging in the RM370,
I was reading an old copy of the "Moto-X Fox Guide to Preparing the RM and PE Suzuki for Competition" booklet the other day and noticed a paragraph under Carburetor and Throttle about altering the ignition timing on the RM370 to help stop the "Ping".
It quoted, "On the RM370 you should change the ignition timing from the factory setting of 4.1mm BTDC to 3.8mm BTDC. Retarding the ignition before top dead centre will give the 370 a little more low end power and help prevent detonation which the 370 engine sometimes suffers from".
It also said the carby jetting for the RM370A,B should be 320 main, Q4 needle jet with the clip in the third from top on the needle.
If any or all of these hasn't been done already, they may be worth a shot.
Hope this helps
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Thanks mate, help appreciated but been there. Cheers.