question Triumph Cam Timing off?

[sexton]

I volunteer at a military museum in Oshawa, Ontario. We have a 1956-ish Triumph TRW. It only has about 500 miles on it. It is running, but badly. I think it's the carb.

 

But one of the young guys here took the timing cover off instead of the clutch cover by mistake so we checked the cam timing, not expecting to find it off. But it was, by 3 or 4 teeth based on the punch dots on the crank and cam gears and the chisel marks on the idle gear. We corrected it but it didn't improve the running. So now I'm second guessing myself. There was no paper gasket sealing the cover, just a reddish RTV. What did Triumph use? Has someone here had the cover off and messed up the timing? Or did Triumph occasionally mess up the gear keyway to punch dot alignment and have to offset the timing marks to correct? (I had a 60's Royal Enfield so I have a very low opinion of British bike quality.)

 

Malcolm

[Ron]

Malcolm I've been following your Carrier problems and you obviously understand engines. But here you have fallen into the trap of starting something without the aid of a workshop manual! Here is a link to a free download.

 

http://www.scribd.com/doc/22255431/Instruction-Manual-for-TRIUMPH-TRW-Mark-2#scribd

 

I've copied page 15 here (Valve timing). Once you set the timing it will go out of sinc for a good few revolutions due to the odd number of teeth. Very likely you have lost the ignition timing now?

 

I don't think you can blame British bike quality here. Ron (UK)

Edited March 7, 2016 by Ron

[sexton]

Ron, I had the manual at the time and used that section. Despite numerous rotations of the crank, the dots never lined up. Closest they came was 3 or 4 teeth off.

 

Scaling off the pic in the manual, the idler gear is 3 times the diameter of the crank gear and 1.5 times the diameter of the cam gear. So the dots will all line up every 6 revolutions of the crank, I believe. I did at least 6 revolutions because I was very surprised the timing was off.

 

Regarding the ignition timing, I used the tie wrap in the plug hole technique to find TDC and confirmed the crank gear dot was pointing at the centreline of the idler gear when at TDC (It looks slightly off in that manual picture, but in real life it does.)

 

So before removing the idler, I turned the crank to TDC firing and locked the distributor gear to prevent it rotating. I then removed the idler and rotated the cam gear as required to get the dots to all line up and replaced the idler gear. Once we got it started (she doesn't like to start) I did a quick check of the ignition timing with an induction timing light and it looked about right, eyeballed at about 20 deg BTDC (engine running at quite high rpm, she also doesn't like to idle) but the light doesn't have the advance feature so I couldn't confirm exactly what it was. Despite the valve timing change, the engine didn't seem to run any better, or worse.

 

If the carb rebuild doesn't fix the problem, and I confirm the ignition timing is OK, I'll pull the timing cover off again and double check the dots.

 

And thanks for the electronic version of manual.

 

Malcolm

[Ron]

OK Malcolm, I don't know if calculating the size of the gears will work like that? I don't have a TRW in my collection, all my bikes are WW2. But I have Velocett's and I only mention these Velo's because they are unusual as they also have the odd number of teeth on the timing gear and those same auto advance units, and from memory it's something like 79 revolutions before the dots line up again. You could recheck this if you pull the cover off again.

 

Regarding the ignition timing. On my side valve singles there is always a removable plug over the piston crown to put a gauge in to check the timing. Something like a drinking straw marked at TDC and then in your case 1/8" further up for the point were the CB points just start to break. Of course you would have to removing the cover to hold the auto advance unit at full advance. Again apart from my Velocett's all mine have a manual advance handlebar lever. It's a shame if the manual doesn't give the piston position at full retard as well. On the Velo's they quote (from memory) something like 7/16" BTDC full advance or TDC at full retard.

 

 

Also not a major job if you have to take the head off to check it properly.

 

I gather from friends who ride TRW's that they are sweet smooth rides!

 

Ron

Edited March 8, 2016 by Ron

[sexton]

Ah, the light is coming on, Ron. Your right, the idler gear can have any number of teeth so it may take many, many turns for the dots to align again. So the valve timing was likely OK.

 

But I still think what I did was OK (if unnecessary). I aligned the dots at TDC and I ensured the ignition timing didn't change relative to TDC.

 

I converted 1/8" below TDC to crank angle and got 25 deg using a conrod length of 6.5" (pure guess, just looking for a ball park figure) and the timing light was showing the timing in that ball park.

 

Anyway, I'll check out the carb and go from there.

 

And the guy working on the bike told me there was no access hole in the head for finding TDC, despite the manual saying there was. I'll double check. Makes sense there would be since they didn't have tie wraps in 1956.

 

Malcolm

Edited March 8, 2016 by sexton

[Ron]

I agree Malcolm. If you re-timed the valves without moving the mag pinion and engine, the ign timing should be as it was before. Assuming it was set correctly in the first place? These are best set statically as per the book. I'll be interested to hear if you get it running nicely. Sometimes it's just down to dirty fuel and/or plugs. Regards Ron

[juan carlos rodriguez]

Hola buscando informacion encontre esta charla del 2016. Tengo una TRW 500 y tambien tengo muchos problemas de encendido. Mi moto llegó (hasta que se paró) pero no iba bien a altas revoluciones. Ahora sin arranca. Estoy ajustando el encendido y el primer problema es ubicar el PMS, porque el orificio de la bujía coincide con la válvula de escape y ahí no puedo llegar al pistón. ¿Cómo es el método que ha utilizado?
El segundo problema es que mi moto parece no llevar acoplado el mecanismo de avance automático al piñón de encendido (piñón número 11 en el despiece oficial de fábrica). Sin avance automático es imposible que la moto funcione bien a altas revoluciones. ¿Conoces algún lugar donde encontrar este mecanismo a la venta? Gracias

 

hola, buscando informacion he encontrado esta charla de 2016. TEngo una TRW 500 y tambien tengo muchos problemas de encendido. Mi moto funcionaba (hasta que dejo de hacerlo) pero no ib a bien en altas revoluciones. Ahora sin arranca. EStoy ajustando el encendido y el promer problema es localizar el TDC, pues el agujero de la bujia coincide con la válvula de escape y por ahí no puedo llegar al pistón. ¿como es el metodo que usted ha usado?
El segundo problema es que mi moto parece no tener el mecanismo de avance automático adosado al piñón del encendido ( piñón número 11 en el despiece oficial de la fabrica). Sin avance automatico es imposible que la moto funcione bien a altas rpm. ¿Saben de algun lugar donde encontrar este mecanismo a la venta?gracias

[Le Prof]

Translation for @juan carlos rodriguez, above.

"Hello looking for information I found this talk from 2016. I have a TRW 500 and I also have many ignition problems. My bike arrived (until it stalled) but it didn't go well at high revs. Now no boot. I'm adjusting the ignition and the first problem is locating TDC, because the spark plug hole coincides with the exhaust valve and I can't get to the piston there. How is the method you have used?

The second problem is that my motorcycle does not seem to have the automatic advance mechanism coupled to the ignition pinion (pinion number 11 in the official factory exploded view). Without automatic advance it is impossible for the bike to work well at high revolutions. Do you know any place to find this mechanism for sale? Thank you"

[sexton]

Juan Carlos, the way I find top dead centre on a side valve engine is to use a large zip tie. I called this a tie wrap in my earlier posts but zip tie is the more common term. Google zip tie to see what I mean. 
Slide the large head of the zip tie into the spark plug hole. Turn the engine over by hand. The piston will hit the head of the zip tie before it reaches TDC and will stop. Using a paint pen, mark that point on the harmonic balancer or fan pulley and also mark a stationary point on the crankcase.

Then turn the engine the opposite direction from the way it normally turns until the piston stops when it hits the zip tie.

Mark that point on the pulley relative to the mark on the crankcase. 
The point exactly half way between these two marks on the pulley is TDC. 
Malcolm

Edited October 24, 2022 by sexton

[juan carlos rodriguez]

bien, muy inteligente. buena idea Gracias. lo haré