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Index > Engine/Drivetrain > Thread: timing difficulties
Thread: timing difficulties
Tom93R1


Redlining
Posts: 458
posted January 17, 2004 11:12 AM

timing difficulties

I have had this timing problem forever on my REPU. It is as though the distributer needs to be turned about 1/2 tooth. I fully advance it and it is too far retarded, so I turn it one tooth and fully retard it and the timing ends up too far advanced. There is a window of about 20 degrees that I cannot get to. It has been like this as long as I have had it on the road and I finally decided I should do something about it. My problem is that I dont know what to do about it. Anybody have any suggestions?
I have an '86 motor, a front cover from who knows what (maybe 12a, maybe 4-port 13b) and a distributor from an 83 rx7. Is it possible that somewhere along the way Mazda changed the orientation of the gear on the distributor? Is there a way to slightly turn the gear on the shaft?
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

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Klaus43


Rotorhead
Posts: 1259
posted January 17, 2004 12:38 PM

On what basis

are you timing it... the mark(s) on your pulley? Static timing or with a light? All vacuum advance disconnected, I take it... any chance the advance mechanism's sticking? I don't know about your '86 motor, or how those bits do/don't interact, but I do know timing specs did change over the years for the various incarnations... and I'd bet that the timing mark on your 'unknown' front cover might have something to do with your dilemma.
How good can you time it to run, (nevermind the mark)?

       
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Tom93R1


Redlining
Posts: 458
posted January 17, 2004 11:31 PM

That estimates of timing changes are based off the pulley, but I am not timing it to the pulley. I am certain the pulley is not an accurate representation of where TDC (or the rotary equivalent of it) is. I am trying to get it timed to where it runs best but I cant quite get there. It is either too advanced or too retarded and I cant get it anywhere inside that 20 degree area. I mean, it still runs all right but I dont think it is as good as it could be.

____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

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dhood


Hauling
Posts: 134
posted January 18, 2004 08:58 PM

My Calif spec 77 started running rough last month and I've been fooling around with the dist and having the same problems. Seems everytime I take out the dist I never get it back in right. Once a dealer mech told me I put it in backwards! but it ran better that way than after he finished with it. The truck sat for a couple of weeks then the float seat stuck and I thought that was the problem, but after cleaning it out, the same thing. Runs like its too far advanced, no power at higher RPM, couldn't get it to idle below 1k. Installed the dist like you did moving the gear one tooth. Too much advance then too much retard. Finally decided the pully could be the wrong pully. About 5 years ago Checkpoint installed this engine, the original was blown up by a joyrider. I had a stock everything, now I have an electronic dist and who knows what else, so am having to feel through this. I've got six notches on the pully, possibly the first is 10 degrees BTC, second is TDC, then 5, 10, 15 and 20 ATC, but I'm just guessing. Stock timing is TDC leading, but when installing the dist if I align the pully to 15 ATC at least I can get it to idle. I also check to make sure the reluctor is aligned with the leading pickup so the rotor is pointing to the L1 tower. By the marks on the pully, it would seem the engine revs best at about 30 degrees BTC. That can't be right. What I'm thinking is there is another problem and compensating the timing to correct something else is not going to make me any happier.

Anyhow, with two or more problems going on at the same time, its hard to diagnose. The carb air and fuel jets don't seem to to do much at 1500 RPM when I turn the screws. I replaced a bunch of hoses, fuel pump, cap, rotor, condenser, coils and plugs, and now waiting for new plug wires to arrive. Dist advance is smooth and works well, so I'm guessing if not the wires, then I'll rebuild the carb again. I'd like to mark my pully for sure, but not knowing how to determine TDC in a rotary is another problem.

       
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rotarydave


Hauling
Posts: 108
posted January 18, 2004 11:58 PM

Be very very careful in what you are doing i think you said it is an 86 engine that you have if so you might get away with what i am telling you, look at your front pulley to determine if the timing marks are in the right location. On an 86 and newer it is relatively easy as the ft pulley only bolts on to the hub one way but if they used the older ft hub with the older pulleys it will bolt any one of 4 ways which will then put TDC by the mark in the wrong location. It can run but this would be why you couldn't get it to the spot you are looking for. We had this problem on an 85 rx7 and swapped everything until I got a hairbrained idea to put the distributor in backwards and it worked, because our marks were off 180 degrees

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Tom93R1


Redlining
Posts: 458
posted January 19, 2004 09:16 AM

I am pretty sure my pulley is on the right way. It is the older style that will fit any one of 4 ways, but if I get the timing off anywhere near 90 on either side it wont run at all or even start. I had it 180 degrees off for emissions, it actually ran cleaner that way. Just didnt run very well and detonated pretty badly. I feel lucky I didnt break any apex seals.

I guess I just need to pull the dist out and look at it a bit more. Maybe I can add to the slot so it will turn a little more, or maybe I can figure out something else.
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

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Klaus43


Rotorhead
Posts: 1259
posted January 19, 2004 10:05 AM

'Add to the slot'???

That doesn't sound like a good idea to me... I'd be very cautious not to exacerbate any issues before being able to 100% confirm what precisely is going on.
For example, if it was running fine up to a point, like your '77, David, I wouldn't think it has anything to do with the timing, nessecarily...

       
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Tom93R1


Redlining
Posts: 458
posted January 19, 2004 10:31 AM

Maybe I could then count the number of teeth on the dist. gear and bust out the old protractor to figure out how many degrees the old adjustment slot is. With that info I should know if the design just leaves a few degrees worth of gaps where timing cannot be adjusted.
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

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Jeff20B


Moderator
Posts: 661
posted January 19, 2004 12:37 PM

I've also seen a timing problem that I couldn't figure out on an '86 engine in a '79 RX-7. Something about the distrubutor drive gear on the E shaft just didn't make sense. The only thing I can think of is the gear was installed backwards because it made no difference how the distributor shaft was oriented when fully seated into the front cover. It always seemed off by just a little bit.

I hope my 20B dizzy project doesn't have this problem.

Tom, you might need to slot your base plate one direction or the other to get it to the 1/2 it needs to be. I don't know of any way to check if the drive gear was installed correctly without removing the front cover. Yes, they can be installed backwards rather easily.
____________
'74 REPU
'76 Cosmo
'77 MG Midget 13B
'81 RX-7

       
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Tom93R1


Redlining
Posts: 458
posted January 22, 2004 03:13 PM

Last night I screwed around with the timing for about an hour, rotated the dizzy tooth by tooth all the way around probably 2 whole times. I also found a vaccuum leak in one of the vaccuum advance hoses which I fixed and a connection from an ignitor to one of the coils possibly not making good contact . Somewhere between those 3 things I managed to get the timing set in the range I wasnt able to get before. Now it runs much more smooth than before but seems alot slower. Oh well, I guess I cannot have both fast and smooth. I probably need to adjust the timing a few more degrees, it is probably just a little more retarded than it could be. I just hope to get it as fast as it was before my emissions testing scandal.
____________


'74 lawn-green
4-port 13b
Weber 48DCO
Racing Beat Header
Magnaflow
resonator/amplifier
really loud!

        Click here to send Tom93R1 an ICQ message. Click here to add 16640317 to your ICQ list. Click here to visit Tom93R1's homepage. Click here to send Tom93R1 an AIM message. 
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