OzVMX Forum
Clubroom => Tech Talk => Topic started by: alexbrown64 on April 05, 2015, 05:51:48 pm
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Hi guys. As some of you are aware, i rebuilt a 79 RM80 for the boy.
First ride out and running it in... lots of spooge, hanging idle, rattle/pinging at idle and a smokey exhaust. I have tried to address problems.
For pinging, i lowered the compression by putting an extra base gasket in, installed a colder plug and richened the jetting. Seems to of quietened it down but still a bit there. Its on its last oversize piston and head has not been matched up. I even had to modify the steel head gasket as it was poking into the bore.
I cleaned the carb 3 times, especially the pilot jet and circuits. Hanging idle nearly gone but not completely and there is still a small bog off idle. The ignition system is weird. I can twist the stator from side of its adjustment to the other and there is hardly a difference. It has the correct stator and rotor. Its hard to get the correct ignition parts for this model but HPI makes a full system thats really cheap. http://www.hpi.be/item.php?item=068K338
Any advice before i go spending heaps of money i dont have? I was thinking of getting the head machined which is $50 at Ian Williams http://www.iwt.com.au/Services.htm Do you think its worth getting an ignition, as i dont know whats happening with this one as its not for this model.
I was also thinking of getting a new pilot jet for the VM28SS and maybe even 1 size bigger. Not sure what else to do as the bike is still sounds like it has a can of nuts and bolts in the head.
Besides that, bike is all good... :)
Cheers,
Alex
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gbox seal knackered, sucking oil and overiding any timing or carb adjustments? sounds like an air leak
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Agree but I would also look at stator side seal..
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I would hope its not a seal, as i just replaced every seal on the bike including both mains. The whole engine is brand new.. new piston, rings, rebore, rod, bearings, seals, carb kit etc. put fresh 98 ron fuel in. Sprayed "start ya bastard" around the place and wasn't getting any response.
Edit: looked up how to make a leak down test kit. Will put one together and test the theory. Always good to confirm that one way or the other. Hopefully, the clutch side is ok, as it means splitting the cases again on the little bike.
Cheers,
Alex
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Could be a main seal or centre gasket. what colour smoke?
gearbox oil can often be off colour if it has a leak to the box and the exhaust stinks
another matter that caught my eye is
Do you think its worth getting an ignition, as i dont know whats happening with this one as its not for this model.
are you saying the CDI is incorrect?if so what is it from ?
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Pay the $50 and sort the cylinder head then buy a timing light and check what the ignition is doing
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Thanks guys. I will get the head done. Fitting 2 base gaskets and using a colder plug quietened it down a bit. I re-checked the ignition and it is the correct one according to numbers, but the timing mark is on the opposite side of the stator to the one in the Suzuki manual. Is there a link to how to check the timing with a timing light. I can do static timing but not sure how to set up timing marks and how to use the light. Am also putting together a leak down kit. The smoke is white, just smells like 2T.
Cheers,
Alex
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white is not good....should be blue I think
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White smoke means you need to break out the spanners unfortunately you have right seal/ Centre gasket issues.
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.....is it possible you put a crank seal in around the wrong way????.....should be spring side in the oil
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Thanks guys.
I will definitely be doing a leak down test. I have ordered a 15psi gauge, so i will do the 6 psi for 6 minutes test. Because i have been testing the bike while idling and its not properly run in (as my main problem has been the pinging) it has been smokey, but i remember when the boy was riding it, there was not smoke... so hope springs eternal. ITDog, you are correct. I went through all my old rebuild pics. When i stripped the bike, the spring was towards the crank. My rebuild pic shows i put the new one back the same way. I understand now that the positive pressure on the oil side helps press against the spring and thus help sealing. It is a double lipped new seal and i have read that people have installed them either way with no adverse affects but i realize my mistake and it may be a factor... thanks for highlighting that.
So... cylinder head sent away tomorrow to try get matched to cylinder with new pilot and reeds to help cure pinging. Also, try to get timing sorted out. Leak down test to determine if i have a main seal leak. If i do, then strip, replace and rebuild.
I will report back on progress....
Cheers,
Alex
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Good luck on finding the fault mate ;)
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Hey Alex, you dont happen to have a spare slide to sell me from your VM36 from your 125k?, I have an IT250K I am restoring and the slide is pretty average (no air filter will do that!)...think it maybe a 2.0?
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Yes, the 250 K had the 2.0 slide ITDog. I had to order a 2.0 from MikuniOz for my 125 VM36 upgrade as the new VM36 comes with a 2.5. He sells them for $55 and has both left and right idle screw slides...http://www.mikunioz.com/product-category/throttle-valves-slides/ He has a new website and you can order online and pay with paypal. Goodluck getting the original jet needle 6f34... thats a rare part. I will be getting a few jets from him again soon. IT250K would be a great bike, seen some of your rebuild on the Yammie forum. You will have to post some pics up of the finished bike.
Cheers,
Alex
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cheers for that.....hope i have more luck with it than my 490 , could never get that to run right :'(
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Maybe there's some bits in here that would be good spares ;)
http://www.gumtree.com.au/s-ad/evanston-park/parts/suzuki-rm-80-motors/1070392345 (http://www.gumtree.com.au/s-ad/evanston-park/parts/suzuki-rm-80-motors/1070392345)
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maybe the xtra base gasket is not the right way to lower you comp as it will raise the port height by around .5mm. just a thought i would look for the cause of the problem described before changing things to much if the engine rebuild is as you say complette maybe something is not just right.
make sure your slide is clean and dry and set the idle so the engine stops when the throttle is closed and the see what happens when you give it a small blip on the throttle see if it snuffs it may also be hard carby rubbers worth a look. even though it a new build have you checked the comp. i take it you did the engine rebuild what crankcase sealant did you use.
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probably not one of the problems-- but had an AX100 suzuki road bike that had sucked the gasket in that seals the reed block to the cylinder base [sucked half of it in leaving a gap]. Totaly mucked up the carburetion but in this case the ax100 is reed only. Goes in what looks like a piston port [but not], then turns 90 degreese & down through a small reed block.