Ultralights Posted February 24, 2007 Share Posted February 24, 2007 well today is the first time i have worked on a 2 stroke engine, the vampire is due for a 150 hr inspection, so far i have successfully inspected the carby's change the needle setting from full lean to something more suitable and managed to re-assemble the carbies. now its onto the piston inspection, ring inspection and replacement and decarbon.. Something i noticed was the oil on the cylinder head, initially i thought it was leaking from the spark plug, as there was a little more than usual rev drop on 1 ignition system, but removing the head had me scratching my head..:clown: the gasket seams to be in good order and the oil appears to be seeping from the head stud ? hmmmmm as i said before, i have never pulled apart or ever worked on a 2 stroke, let a lone a Rotax 503. anyway, it obvious a little de-carbonising is in order... now how do you do that?? (thats a serious question by the way) tomorrow i will be removing the cylinder barrels to check the piston rings, rod and crankshaft bearings... any other tips from people with experience with the Rotax 503 would be greatly appreciated.. oh and spark plugs will be replace with what came out of it.... B8EGV type. the head didnt look the best either as a result of the oil seeping the other one didn't look too bad.. what could be causing the seeping? is it normal? leaking gasket? though getting to this point trouble free would not be possible without the help of Keith Rule and other from the hunter flying club... thank you guys! its very much appreciated... Link to comment Share on other sites More sharing options...
Guest micgrace Posted February 25, 2007 Share Posted February 25, 2007 Hi Looks good. I suppose the oil present is working up from the crankcase up the stud over a period of time. No concern really. If really fastidious I suppose you could use some thread sealant on the studs. Gives the impression one cylinder is running a bit leaner than the other, but since you attented to the carbs that should cure it. I notice in the upper right hand corner of the engine photo an auto type fuel filter. Get rid of it, these block up with 2 stoke mix. Apparently the oil reacts with the paper element causing it to expand and close the pore space Use one of those clear glass ones with screens that may be seen on Drifters and such and mount it well. As for decarboning. Only remove the carbon on top with some sort of scraper/brush and don't nick it. DONT touch the skirts except to wash them. Nulon throttle body cleaner seems to work very well to dissolve muck. A broken ring will do to clean out the ring grooves. Don't get carried away and leave marks/gouges in the aluminium. If the bores are slightly gouged/marked local motorcylcle shop should do a hone in the clyinders. If good, I wouldn't hone the rings will seat soon enough. When you get them back, scrub well with detergent and water on the bore wall, then use a rag with some oil to clean the wall. When it comes out clean thats it. Pay very close attention to the gudgeon pin/bearings. If in doubt get some new pistons/pin/brg etc. This is critical. Micgrace Link to comment Share on other sites More sharing options...
Ultralights Posted February 25, 2007 Author Share Posted February 25, 2007 that filter in the top of the pic is on the gearbox breather tube. Link to comment Share on other sites More sharing options...
Yenn Posted February 25, 2007 Share Posted February 25, 2007 Once you pull the cylinders off the pistons in my opinion you are committrd to putting in new rings and I think it would be false economy to not give the cylinders a very light honing to provide a cross hatched finish. This will aid the bedding in process and I believe it is stipulated in the Rotax engine notes. If you are putting in new rings you will have to ckean up the top edge of the piston as the rings are "Dykes " rings, which means they are at the very top of the piston and gas pressure is useed to help seal them against the cylinder. As for the oil leaking into the area, you will have to have a good look at wherever it coiuld come from. Good luck with the break in, it is boring and terribly noisy. Link to comment Share on other sites More sharing options...
Guest micgrace Posted February 26, 2007 Share Posted February 26, 2007 Hi Couldn't quite make out the filter use from the photo> Good luck with the rebuild. Hope that bit of info was of some help. Micgrace Link to comment Share on other sites More sharing options...
Ultralights Posted February 26, 2007 Author Share Posted February 26, 2007 every little bit helps, i am waiting on spares, so when they arrive i will get back into it, hopefully a few hrs after work during the week, as i have a bucks weekend planned for next weekend.. Link to comment Share on other sites More sharing options...
Guest Nickjaxe Posted November 9, 2008 Share Posted November 9, 2008 I have had that leaking oil prob on my 503, it come from the metal sealing ring the thing that does the job of the head gasket, If somebody in the past has had the head skimmed they can take to much off and the grove in the head the ones that seal onto the ring become to shallow to bite into the metal rings, I had that prob and needed to go arond them with a sharp tool being careful not to scratch the sealing surface, There are some dodgy non rotax rings about, the rotax ones are alloy over steel, the fakes are just alloy. Nick. P.S. I know this is an old post but it may help others. Link to comment Share on other sites More sharing options...
icebob Posted November 10, 2008 Share Posted November 10, 2008 Hi, Nick may have it for you, on the photo of the head have a look in the 7 to 9 o'clock position at the seal and your "good" cylinder head at the 8 o'clock position, it looks like the start of a leakage there too. May be just shadows but both seals look suspect. Bob. Link to comment Share on other sites More sharing options...
jetboy Posted November 10, 2008 Share Posted November 10, 2008 Download all the chapters "care and feeding of the rotax" from CPS (california Power Systems) or airwolf by Mike Stratman you are bound to find something important there. I've maintained a couple of 503 but not seen the oil stains pictured. Yes if there are any pits in the needle roller bearings or wrist pin distress - blueing etc. its going to be goodnight nurse in short order. Been there done that. Your model will use cageless needles - should be OK, main defect is likely stuck rings, 503 is the best 2 stroke Rotax made, IMHO Ralph Link to comment Share on other sites More sharing options...
Guest Lee Schaumberg Posted November 14, 2008 Share Posted November 14, 2008 Oil Seeping Hello and answer for engine owner. The dried and burnt oil on the head and cylinder is coming up from the crankcase. To prevent this you have to seal the head studs at the cylinder base. This prevents the fuel/oil mix from working up to and out the head nuts. Make certain that only a good 2 stroke oil is used at the proper ratio. Back in the early 80s I used 50/1 in a premix 500cc suzuki running at 8500 rpm. After about 5 hours I ran amzoil at 100/1. My pistons or heads never were black. The gyro was run 150 or so hours and I still have it some where. The best way to clean up the castings is with a fluid that dissolves the black stuff. I can't remember what its called. Your 503 is a lot better engine. My engine powered a Bensen gyrocopter. Yes I was that crazy back then. Link to comment Share on other sites More sharing options...
facthunter Posted November 14, 2008 Share Posted November 14, 2008 more on 503. Some of the circlips are too soft, check them out. Sometimes the curled up end of the circlip prevents it seating properly and the only thing to do is cut or grind the end off. If you locate the clip so that it allows the small "key" groove available to prise the circlip out it will be removeable next time. Getting the gudgeon pins in without dislodging the needle rollers takes a bit of care . You must ensure that none are dislodged and drop into the crankcase. I would suggest that you get a bar of steel machined with a good finish to about two thou. under the gudgeon size, so that it goes in easily as a "dummy" pin and then displace it with the proper pin. This way the rollers are never able to be dislodged. Cleaning the ring grooves out can be a difficult job. particularly the top one, as the carbon can be very hard. It is probably too late now as you may have ordered the rings, but I find cleaning the carbon out of the grooves can be such a chore that I would recommend getting the piston assy rather than just the rings as they were better value , especially if you take your time into account. I like to polish the piston top and combustion chamber as the carbon does not form so quickly and they run a bit cooler. (piston temp). Nev... Link to comment Share on other sites More sharing options...
Guest Nickjaxe Posted November 14, 2008 Share Posted November 14, 2008 To help me with my 503 maintenance I got the CPS DVD set money well spent invaluable for stripping and re-building the 503. Nick. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now