I need to know how to find true TDC on the rotary.
My E-Shaft does not have timing marks, and if it did they would be wrong because the pully was removed and moved around. So if someone could please let me know some different processes to time this thing right. Pics would be nice. I am having a heck of a time to get the fuel mixture right, it is burning way rich. Its a Weber setup by the way. I know the carb is functioning properly, but the timing is off, and I need to know how to find TDC when all is lost timing mark wise. Yes I have used the search button, and I get the same results. Please take pity on me I need to get this thing timed right. I got some races coming up this weekend, and I need to kick some tail. I already took it for a test drive, and man it runs like a beast, but it burns way too rich.

 

I find it funny that this question has been asked but never really answered. I don't really know where "Top Dead Centre" would be on an engine which has no "top" or "bottom" of the orbital motion of the rotor, but I know we use the term anyway.

How to find it? Gah... Well, the only ways I know all involve either timing marks (which you don't have) or positioning when re-assembling the engine (which isn't apart in your case).

If someone knows another accurate way of re-making timing marks, or if there's been a thread that I've missed, I'd love to see it.

Jon

 

Can't you remove top plug and center the top of rotor in plug hole ( use penlight ) and then mark the pulley ? Would it matter which lobe of the font rotor is designated as TDC as long as the dizzy is synched with it ?

 

As for never really answered...aint that the truth. Alot of people touch on the subject, but noone ever answers it. I have heard a few ways to do this. There has to be some kind of mark not just on the pulley to determine TDC. The problem I have found is that the Rotors dont spin perfected level they kind of lob around the inside. This makes it kinda difficult to just peak in the front plugs and see if the rotor dimple is there. If you take the back plugs out and watch for seals and then line up halfway between them. You still only get a rough shot of TDC. and without timing marks its a little hard to use a light to get it just right.

 

Ok, this one is easy. first take the front half of the front pulley off - this is the thing that's held on by 4-10mm bolts. Now remove both plugs off the front rotor and find a small screwdriver or suitable poking device that fits through both holes and into the chamber (note that the trailing plug is much smaller than the leading). Now you kinda poke in there till you hit the face of the rotor and note the distance. Then turn the shaft, then poke some more. When the distance to the rotor is almost the same for both holes you know you're close to TDC, so take the front half of the pulley and bolt it back on in the position that is the closest to lining up the timing marks on the pulley with the timing pin in the front cover. Now you can turn the shaft to the first timing mark and that's TDC. Poke around and make sure you got it right, then put your plugs back in.

Pretty easy, right?

 

the pulley is keyed so assuming you have a pulley it only goes on one way. unless of course stock pulley's have some way of getting out of alignment with the key. the other problem would be the marks being MIA on the pulley.

 

Okay what about this. Every motor has a tdc and btc. The dizzy rotor has an arrow on one side. I have found that the arrow can 180 out from it self with one full revolution of the motor. So I would guess, and have been tring to determine, that the arrow should point at the L1 at top dead center. But where should the rotors be? And how do I know?

 

there is another trick to finding a TDC without taking off the pulley, but I wil wait til someone figures it out. consider this a test.

 

Oh thank you Jedi Master. LOL

 

wacky is this by chance an old boinger trick?

 

no boinger trick, but just an old school trick using the grooves in back of the flywheel. then line them up with the rear side plates, but of course, you have to remove the inspection plate to see.

 

Just to clarify since some posters don't seem to know: the front pulley comes apart in two sections. One section stays attached to the motor and contains the keyway and is held on by the 19mm bolt, the other section has the grooves for the belts and the marks for the timing and is held to the other section by four 10mm bolts. This allows the timing marks to be clocked in 90 degree increments via the four bolt positions with no safegaurds against misalignment.

I just read the guy's post again, and he says there are no timing marks. Clean the front pulley, unless someone removed them with a grinder, they are there, just hidden by years of grime.

 

do the rotor trick mentioned above. that's how i found tdc and my timing is dead on now. woot

 

wacky I tried the line up the dimples under the inspection plate thing. Maybe Im a little handicapped, and did it wrong, but that didnt work....You got any pics of these dimples or at least a description of them to make sure I used the right one. I mean i have it timed pretty close, but i want it to be right on par so it idles smooth, and doest burn so rich. I dont want to carbon lock this motor up.

 

So i removed the pulley again today and chemically stripped all the paint and grease of it. I rotated the pulley in my hands after cleaning, and two very faint scratches caught my eye. So I took out my dremel and marked them up a little to make them more noticable(maybe 1/16 of an inch deep). I repainted the pulley and painted the timing marks white. Now on may trashed engine there is a key that holds the inner most pulley to the mount. On my good engine, no such key, I didnt removed the big 19mm bolt only the 2 pulleys held on by the 4 10mm bolts. Since I only need the inner 2 groove pulley for my alternator, and water pump. I am gonna scrap the outer pulley. now since there is no safeguard for correct alignment should I just time the 1st pulley mark to the T1. See if it fires, and just keep removing and rotating the pulley, and realigning the T1, until it fires right. Ok maybe thats too much work there, I should do the screwdriver poke trick until I get close and then align the bolts up and finalize the correct position.

 

if the keyway in the front of the e-shaft is about at 9-oclock... bolt on the main pulley so the marks are straight up..

this is where TDC is for timing purposes on a rotary.

 

yes, put the key at 9 O'clock, that's what i read at nopistons. that should be TDC.

wackyracer ~
maybe i'm just tired or too dense, but could you run that flywheel thing by me one more time?

 

The problem with that method is that you must remove the 19mm bolt to see the keyway. Not only is this bolt normally difficult to remove on older motors, but you risk the pulley popping off the end of the shaft, which could result in the needle bearings slipping out of position in the stack.

If anyone does attempt it by this method, take the precaution of a 2x4' holding your clutch down - this preloads the e-shaft and makes it just a smidge harder to mess up the positioning of your needle bearings if the pulley happens to fall off after you remove the bolt..

 

here's the pic from mazdatrix. Assuming its installed in the engine. the area without the groove should line up with the inspection area in the rear side housing. its early in the monring & I need more coffee. hell let me know and I will take a pix since I will be installing a bridgeport in a RX-3.

 

On the side note, if anyone is interested in doing ur own timing marks per YAW, be very careful as the leading timing mark in the pulley is NOT in TDC or "0"

 

yup. thats where 0 is. The only pulley where you cant go wrong is on the pre-81 motors wherein there is a notch on the face of the pulley. You have to chisel that out, in addition to the 4 bolts, to separate the pulley.

 

there is no need to remove the front hub.

throw an inspection mirror in there or feel for it with a pick.. you can usually find it with the front bolt still on.

 

that is what i was thinking... theres only 4 positions u can put the front pully on... so its only natural that if u have it roughly close to TDC u could put the pulley on in that position and then line it up exactly TDC..

 

I waited but since no one commented, then I will. The first mark is not a TDC. Read the label in ur hood - usually, timing is 10L.

 

Ok I followed wacky's advice, and I found TDC by lining up the flywheel in the inspection plate. I aligned the Dizzy to L1 and gave it a whirl. FIred right up, but now there is a new problem:

When cranking egine, engine fires right up, when I lay off the KEY to disengage the starter the engine quickly dies. Upon initial cranking the tach does not respond and then all the sudden the tach jumps to match the RPM, and the engine dies. Almost like all spark is lost after the starter is disengaged. If I intentionally adjust the dizzy to way off time the engine will start and run really rough, you know timing is way out by then, but it maintains spark. WTF? Anyone ever heard of this before?

I heard the tach is measured by the trailing spark. SO if there is no trailing spark then the tach should not respond.