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Discussion Starter #1
Still unable to get my 1970 t120r started after build. It was in an unknown state from an owner who died while working on it, 5-6 years ago. Have put in Boyer ignition(am getting good spark at the spark plugs), cleaned the carbs, new rings, honed the cylinders, valves and valve guides, ground the valve seats. I believe the valves and timing are set correctly. However, When I kick start it, I'm getting blowback through the carb. Also, I'm not reading any compression.
 

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Remove the plugs, look through the plug holes and check the valves are opening and closing. [valve stuck open?]
If you are sure the ign. timing is OK, it only leaves fuel or possibly valve timing.
 

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how did you time it?

if you used the timing hole, did you hit the TDC slot instead? (not sure if the 70 will have 2 slots?) if you did, it will spark at the wrong time.
 

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Discussion Starter #4
Valves working OK

I have the rocker arm covers off and can see the valves moving up and down. Also, I can look into the cylinder spark plug holes and can see the intake valve opening and closing.
I timed it using the timing plug and the tool. I found TDC watching the intake valve, and saw the tool dip. Then I backed up slowly and watched fo the second dip. That should be 38 BTDC.

I can understand no compression because of the new rings. But I don't understand the blowback through the carbs. How would timing and blowback be connected?
 

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Discussion Starter #5
Also, I put a very small amount of gas into the spark plug hold on the right cylinder then kicked it over. I saw some flame come out of the right carb.
 

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I had similar symptoms after my rebuild.
To cut a long story short, it was a combination of electrical and fuel delivery.
It was sparking multiple times, because the EI rotor was fouling the stator, and hence the timing got progressively worse.
The fuel level in the carb bowls was adjusted so that the floats were higher (richer).
It appears that its important that the inlet is connected up to the air filters. [standard], to begin with.
And the recomended jetting.

Its very frustating when everything appears to be OK, takes determination and patience and the valuable assistance from the guys here.

So the diagnosis for flames and smoke from the inlet was weak mixture and spark timing, and maybe air leaks from the inlet set-up.

The saga is here:
http://www.triumphrat.net/members-restoration-and-rebuild-projects/119014-dave-s-caulky-74-t120v-rebuild-24.html
 

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Zero compression can only mean the valves are opening at the wrong point.
Pop off the timing cover and retime the cams. Don't just try and rotate 10000 times to see if the lines ever line up, it's easier just to pull the middle wheel and then line everything up. There's will be some spring tension to deal with on the cam wheels, but at least you'll know it's right and the inlet cam won't be opening just after BDT. Hopefully you haven't bounced a piston off a valve.

If it's not the problem, all it cost was time and a timing cover gasket.
 

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Discussion Starter #10
Cam Timing

I relooked at the Boyer Timing Plate to ensure it was on right (clockwise pointing clockwise).
Rechecked the timing.
I watched the intake valve on the right side, and when it was closed I saw the timing plug pointer dip. I then backed off until it dipped again (the intake valve was opening) and affirmed that it was at the 38 degree BTDC.
I then took the timing cover. I see all the little marks on the intermediate wheel, the crankshaft gear, and the exhaust and intake gears. I see where in the service manual it says they only align every 94th revolution, but sure can't figure out how you figure out if they're aligned correctly or not.
Emanthehorse: how do you pull the intermediate wheel off so you can align all the gears?
 

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Discussion Starter #11
OK - K see the intermediate wheel is held on the by the timing case cover.
So if I pull it off (I'll have the crankcase gear pointer straight up and locked so it won't move) - I will be able to move the intake and exhaust gears to align all the pointers?
Just being very cautious - I don't want to take the gear off and really screw things up!
 

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Trying to adjust & re time the valve timing with the rocker boxes in position might be difficult if not impossible as you will be fighting valve spring pressure trying to turn, line up & re time the gears. Removing the rocker boxes should allow the gears to be rotated easily.

Ideally, you'd be better off re checking & lining everything up again from scratch. The Triumph manual (Page B33) states that before you fit the cam gears you must rotate the camshafts so that the key way slots "are directly opposite" the timing marks on the intermediate wheel when the intermediate wheel mark (double dash) is aligned with the crank gear dot.

Once you have the intermediate wheel set & timed to the crank gear as mentioned above and both camshaft key way slots directly opposite the intermediate wheel timing marks, you can fit the cam gears remembering to align the inlet cam gear DOT with the LONG dash on the intermediate gear. (T120 & TR6) All you need to do now is align the dot on the exhaust cam gear with the DOT on the intermediate gear & that's it.
 

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I relooked at the Boyer Timing Plate to ensure it was on right (clockwise pointing clockwise).
Rechecked the timing.
I watched the intake valve on the right side, and when it was closed I saw the timing plug pointer dip. I then backed off until it dipped again (the intake valve was opening) and affirmed that it was at the 38 degree BTDC.
I then took the timing cover. I see all the little marks on the intermediate wheel, the crankshaft gear, and the exhaust and intake gears. I see where in the service manual it says they only align every 94th revolution, but sure can't figure out how you figure out if they're aligned correctly or not.
Emanthehorse: how do you pull the intermediate wheel off so you can align all the gears?

In order to set the static timing, first you need to find TDC.
With the plugs out and rear wheel raised, in gear, look through the plug-hole and see when the piston is coming up to top dead centre.
Push onto the tool in the timing hole and turn the rear wheel forwards until the tool drops into the flywheel slot. [TDC].
Lift the tool and turn the rear wheel backwards slightly.
Finger on the tool again, turn the rear backwards until it falls into the other slot.
This is the timing mark.
Now set-up your EI so that the rotor mark is in the correct window hole on the stator.
(Dont forget to remove the tool from behind the barrels.)
Then strobe it.

This may help...its for the Sparx EI, but they are similar:

You wont be able to set the valve timing pinions with the rocker boxes on.
 

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Ideally, you'd be better off re checking & lining everything up again from scratch. The Triumph manual (Page B33) states that before you fit the cam gears you must rotate the camshafts so that the key way slots "are directly opposite" the timing marks on the intermediate wheel when the intermediate wheel mark (double dash) is aligned with the crank gear dot.
"the camshaft pinions located by means of the keyway directly opposite the timing mark"is actually misleading.The pinion is on the crankshaft;the gears on the camshafts are camwheels.The standard keyway in a camwheel is the one closest to,or adjacent to,the timing mark on the camwheel.The standard keyway is not "directly opposite" the timing mark,no keyway is.

In the words of the manual "The valve timing will be sufficiently accurate - - - - used under normal conditions."That means it will start and run,and cause no harm.
It doesn't mean the timing will be perfect;that's why you have two alternative keyways.If someone has used an alternative keyway,it has most likely been done for good reason.You should try it first.

The keyway on the camshaft will still point toward the intermediate wheel timing mark,regardless of which camwheel keyway is used.The timing mark on the camwheel just becomes useless if timing has been corrected by using an alterative keyway.If for example,you checked the timing with a degree wheel and found the exhaust cam 3 or 4 degrees retarded,you would get better results if you advanced it 4.8 degrees by using an alternative keyway.
 

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Mr Pete: Agreed, the manual does mention "pinion" instead of cam wheel. Not sure what you mean by "two alternative key ways" my cams including my spares (1966) have one key way ?
 

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The cams have only one keyway.The camwheels have 3 keyways.
If the standard keyway in the camwheel doesn't give you the timing you'd like,you can use the alternative keyways to advance or retard the timing by 4.8 degrees (equal to 1/3 tooth increments of the camwheel).If you use an alternative keyway,you can't use the standard timing mark on the camwheel.
 

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An interesting and ingenious cam drive system Mr Pete, they thought of everything. Old Jag engines have a similar Vernier type adjustment mechanism on their cam wheels to give precise timing, thanks for the info .....
 
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