Timing a Rotax single video

GaWajn
Here is a video I made that shows a method to adjust the timing on a Rotax single cylinder engine with an internal ignition coil.
youtu.be/CAqjGYNylyA
The information contained in this video comes from the good folks on this board. Without their willingness to share their knowledge ... I could never have made this video.


Elan Dude
Thanks for posting the video. Very informative.


paulcloutier
Hello...
When do we do this adjustment on an engine ?


GaWajn
When you rebuild it ... or when you suspect that the engine is mistimed and causing poor operation ...


webmaster
Man, that is an awesome video. I'm going to put it up on the web site at "THE NEW SITE "  under Ignition Related to help others.
Others need to see this!!!

GREAT JOB!!!


oly_man
quoting paulcloutier:
A good sign is if its hard to start, and/or it backfires through the carb.


sledrat
I subscribed to you on youtube
thanks man great video!
very helpful!


Bones
I fear GaWajn will soon no longer be a member of our board.....He will be in HOLLYWOOD writing and directing movies

Great job.
Bones


GaWajn
Thanks for the kind words folks ... but I think I will be on this board till I ain't dooin' it no mo'!
When I came here, I knew practically nothing about old Ski Doo's. Now I consider myself past the novice stage, and I owe that mostly to the members of this forum. Still learning too
You are a great bunch and very generous with sharing your knowledge and that is why I consider this place THE vintage Ski Doo ''Go To'' site on the internet!


OldSkiDoo
Great video and very informative. I just have 1 question. In my service manual it states that any single prior to 1968 (Exception to the 165 cam is fixed) you check the timing with the cam fully advanced. 68 and up you check with the cam in the fully retarded position. Cam released according to the marks on the fan housing. It gives a spec of 0.150-0.170 in the condensed service data. Is that only the spec used with the fan housing removed and the use of the dial indicator and advance the cam? Or no.


GaWajn
I never use marks or info from the fan housing.
The only information I have ever used is the info found in the BOMBARDIER service manuals. Every one I have ever timed so far has asked for the advance timing lever to be in the advanced position.
Specifically ... what engine (model and year) are you trying to time?


OldSkiDoo
1970, 299cc. Its just a little confusing because it doesn't state if using the specs of 0.150-0.170 if that's with the head removed and dial indicator mounted. you advance the cam. Or leave the cam alone and time it with the housing pointer. But it does say to leave it in the Retarded position. I left it alone and timed it with the marks. Set the points at 16 thow. It runs perfect. I didn't want to pull the fan hosing and head Etc. But I do have a 335 that im building and the head will be removed. I have a Doo book I just cant remember where I put it. Ill have to try to find it and compare specs.


GaWajn
The video in this thread was meant as a guide to show how to time your single cylinder Rotax engine, in the most acurate way ... as specified in the 1970-79 service manual. With the head off ... or with the head on ... it doesn't change the acuracy of the method. Using a dial gauge without the head on ... or doing it through the plug hole with a dial gauge (direct method ... plug hole straight ... not angled) yeilds the same results and use the same timing specifications.

If you used the fan housing pointer and it worked out good for you ... then you need not procede with anything else. The dial gauge method is good even if you have a different fan housing than what would be original to the engine ... which could lead to different results.

I have scoured all my written material (Bombardier service manuals), and can't find a reference to NOT advancing the lever when timing with a dial gauge. Maybe someone else can chime in here, that has more/better experience than I do. If you advance or not using the fan housing ... I have no idea ... I did not make the video to time using the fan housing way.

The dial gauge method is supposedly more a more acurate way of timing your engine.
www.vintagesnow.com/Ski-Doo_files/skidoo.pdf

That is the manual I use most of the time.
Starting at page 22 ... through page 28 give you just about all the information you should need.
Your 299 should be timed between .147 and .167 BTDC with the lever in the advanced position.
A 335 should be between .160 and .180 ... again with the lever in the advanced position.
These are direct specifications (non angled plug hole).

Whichever method you use ... if you are getting results and a good running engine ... then keep doing what you are doing. It's all good


nanookqc
Is it the same procedure for pre-1970 rotax. I have a 1964 247cc who might be in need of timing? and no black wire coming out.
Rob


GaWajn
The black wire is connected to the points. On your engine, you have no black wire ... therefore I assume that your sled has no ignition key either ... which is what the black wire would mostly be used for. If you have a wire going to a kill switch ... use that one ... should work the same way.

You can temporarily connect one to the points terminal, and feed it though the plug wire hole of the crankcase, or through the hole in the magneto. That should work.
Or ... if you have some kind of very small insulated clip that you can connect to the points terminal ... through the magneto flywheel ... but that might prove difficult.

The procedure will be the same if you can get a connection ... some way ... to the points terminal.


nanookqc
And what. would be the advance for a 1964 247cc? Can't find any info on engine before 1970!
Thanks! Rob


GaWajn
If the magneto has an advance lever ... then I would assume that the spec would be from .150 to .170 thousanths BTDC with the advance lever in the advanced position.
Never done a 64 ... so this is my best guess ... sorry I can't be of more help.
Maybe someone else can chime in and share their knowledge about the earlier Rotax engines?


nanookqc
Just tried 155 thousand before tdc with advance lever and it's running awful. I've check the timing before changing it it's was nearly 200 btdc. But the engine was four storking each time i let go of the throttle. Now it does'nt four stroke as much but it's shakin like hell and when i accelerate it hesitate ans accelerate slowly, still four stroking sometime. i' m a bot confuse and don't know ehre to go from here?


GaWajn
I have no solution for you on this. I hope someone with real world experience with your engine will step in and help you with your problem.
I would encourage you to start a new thread because some people may not be reading the pinned threads. You may get a better response with a new one.


Bomba-doo
I have a 1973 elan with electric start. I am assuming the motor is original?? It has the timing advance lever on it. In the video link in this thread the lever is operated to set the timing. I have a repair manual for ski-doo for 1970 to 77? (I think 77, maybe 78) In the timing adjustment for a single cylinder, it does not mention anything about moving the timing advance lever to set. My question is, do I, or do I not advance the lever to set timing? Will it matter alot? Right now, its seems to be timed without the lever advanced.


GaWajn
There are many people out there with differing views on timing. I have taken my method from a Bombardier service manual. The lever is to be in the advanced position for timing.

1974 Service Manual:
Section ... sub section 4 (engine timing) ... engine timing one cylinder (page 2) ...

''7. Rotate magneto counter-clockwise until specified piston position before top dead denter is reached. Hold advance mechanism centrifugal lever in full advance position (toward magneto rim)''
... the typo is directly from the book ...