503dcdi timing

[zs wbo]

i bought a so called recon 503dcdi on this forum a while ago and it turned out to be a bad buy, whilst i have sorted out most of the problems, one problem still persists and i cant get my head around it, prehaps a fresh mind may see what im missing, TIMING i have the correct timing gauge, with the bearing on the end of the extension to allow smooth opperation in the 30 degree ofset, with the gauge inserted in the mag plug hole i bring that piston to tdc , zero the gauge then turn the motor back to approx 080 [thou] then turn it forwads [direction of rotation] untill the gauge reads 069[thou] BTDC . the triggers are then supposed to be adjusted , the left side [exhaurst side] to align with the top of the pick up on flywheel and the right side [carb side] to align with the bottom of the pickup on the flywheel. this is where the problem comes in, both triggers are 15mm of the mark, and there is not that much adjustment on the triggers, i have repeated the process on the pto plug hole and get excactly the same result. now i know that rotax changed from fixed timing [ early models] to adjustable timing [later models] did rotax change timing covers [the cover that the triggers bolt on to] or could the nose on my crankshaft be be out of align i suspect the latter, however i would be intrested to hear from those in the know

[nicow]

Give Alex Rudd a call-he'll be able to help you...

[nickjaxe]

I found the dial gauge method to hit and miss...I use a 360 deg protractor to get the 16 BTDC setting as per the Rotax spec...see photo,

My protractor is an off old boat plotter but most protractor of around that size work...loads on ebay or print your own,

If your interested in my idea I will give you some more info req like how to find TDC spot on which is req.

Nick.

[zs wbo]

thanks for your reply, i would like all the imformation i can get, iam busy sorting out a protracter as you recomend. using the dial gauge to get tdc ? i can now see [ by your picture ] that i have one new type trigger and one old type trigger that has been slotted to adjust , im going to replace it with a new type trigger , any ideai where i can find a good second trigger,[ the one with the long wire ] otherwise ill just have to pay the bucks at rotax. again thanks for the picture, its been a gtrat help . george

[nickjaxe]

You have to make your own marks on the engine case...you maybe able to see mine in black ink marker,

Not sure if the dial gauge is accurate enough to get TDC spot on....there is a slight null zone at TDC and botom DC,

I use an old spark plug with the guts drilled out and a small nut/bolt screwed in....its supposed to contact the piston head when turning by hand...thickness of bolt head needs to be adjusted to suit...I used washers under the bolt to adjust....

If you want more info just ask.

[zs wbo]

i went out and bought a protracter this morning , i can now see how hit and miss the dial gauge is. thanks very much for your advice, im going to buy one new type adjustable trigger and then all should be good thanks george

[nickjaxe]

Yes if you make a modified spark plug up like I use...and it needs fine adjustment with washers under the bolt head....fully insert it and by hand turn the engine over...you need to adjust the plug and its bolt head so it contacts the piston near the top of its travel...when it stops make a mark in a suitable place on the engine so you can line the mark up with the protractor which should be fitted to the crank end with a suitable screw inserted in the small hole in the centre of the flywheel,

Turn the engine then in the opposite direction again till the piston contacts the modified spark plug and make another make mark on the engine in-line again with the protractor...dissect these 2 marks that you have made with a set of dividers....midway between the marks is top dead centre,

Turn the engine till a point you choose on the protractor is in line with this TDC mark then turn it backward 16 degs...it should now be at 16degs BTDC,

Hope I have explained that correctly...but its a few years since I last did mine....but I'm sure you get the idea,

The triggers just need setting with the engine in this position.