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Old 05-14-2015, 06:33 PM   #1
chiccogarz
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Default Triumph T120 cold start after engine rebuilt

Hi All,

I have rebuilt the engine of my T120r 1970 and I am currently facing some issues in running the engine when cold. I am experiencing something that never happened to my motorbikes and I really need some help from more expert people.

When I kick to run the engine, the kicker goes down without the usual feeling of compressions of the engine. What I did was to open the valve inspection cover an see if the valve were opening and closing properly.

I saw that as this happens with the kicker, the valve move very little or nothing. If I kick more the compression seems normal and valves move as usual. When I remove the spark plugs and I kick the valves move sync and everything seems right. As I put the plugs back and compressions sets the issue comes back again.

What is weird is that as I the engine is warm, the compression is right and I need one kick to start the engine.

I set everything up:
- timing
- valve clearence
- new carbs

but I could not solve the issue.

Does anyone have experience anything like this?
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Old 05-14-2015, 06:35 PM   #2
vorhese
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Default Re: Triumph T120 cold start after engine rebuilt

Clutch is adjusted too tight? Plates aren't making enough contact to move the primary chain?
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Old 05-14-2015, 08:03 PM   #3
Rob Axel
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Default Re: Triumph T120 cold start after engine rebuilt

Yup +1^^^^^^
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Old 05-15-2015, 03:40 AM   #4
'59
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Default Re: Triumph T120 cold start after engine rebuilt

is that not the other way around or am I trying to think too early in the AM ; sounds like the clutch is slipping, not enough compression on the clutch springs.

also check oil correct and level.

if none of these it's too early and i'm going back to my rack.

edit: oh right, I get it ; center adjuster is screwed down too tight and not backed off from the clutch push rod' Yeah, wot they /\/\ said, ignore my comment.

Last edited by '59; 05-15-2015 at 03:45 AM. Reason: hard of thought
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Old 05-15-2015, 04:13 AM   #5
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Default Re: Triumph T120 cold start after engine rebuilt

How did you start it from cold to get it warm?
lots of kicking? bump start or lucky kick?
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Old 05-15-2015, 02:37 PM   #6
Rob Axel
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Default Re: Triumph T120 cold start after engine rebuilt

^^^^Im thinking the plates maybe sticking on "cold" starts...Just enough to keep them from slipping...
Grabbing the clutch and "kicking" my plates free is a habit I have gottn into....I hate hearing the gears "grind" getting it into 1st on a cold start when they are stuck...
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Old 05-15-2015, 05:19 PM   #7
oilfield money
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Default Re: Triumph T120 cold start after engine rebuilt

I used to use a strap with a buckle to engage the clutch plates to prevent this ,But just learned a neat little trick and just carry a bolt with some 5/16 hose over the threads in my pocket and drop it in the clutch lever mechanism to keep the plates separated . That first gear clunck is a little un nerving and they all stick I dont care what combo you go with
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Old 05-15-2015, 06:27 PM   #8
chiccogarz
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Default Re: Triumph T120 cold start after engine rebuilt

It seems like you all think of the clutch.

Anyway, I can make it start after 5/10 mins of kicking. After warming up runs nice and smooth.

I will remove the cover and check the clutch. Should I check something in particular?
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Old 05-15-2015, 07:57 PM   #9
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Default Re: Triumph T120 cold start after engine rebuilt

before you take the cover off, try adjusting the free play in the push rod first.

1) loosen the cable adjusters so the cable is slack

2) unscrew the big round slotted plug in the side of the primary cover.

3) use a socket wrench to loosen the lock nut on the pressure plate inside.

4) use a screwdriver to adjust the center screw so that there is no slack and the pressure plate just barely begins to lift.

5) back the screw off one half-turn so nothing is rubbing.

6) use a pair of vise grips on your socket to re-tighten the lock nut while holding the screw still with a screwdriver through the hole in the socket

7) tighten the cable adjuster to wherever you like it.

if the screw was too tight, then adjusting it this way will let the pressure plate hold the plates together so that the clutch works properly. if it doesn't help you need to take the primary cover off and have a look at the three springs to see that they are tightened enough, and evenly.
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Old 05-16-2015, 04:37 AM   #10
'59
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Default Re: Triumph T120 cold start after engine rebuilt

...and has it been said to check the pressure plate is lifting nice and evenly, I engage the clutch and kick over, either have a dial gauge on the pressure plate surface or even a sharpie mounted to show high points (aim to get a very fine even line all around the plate) .
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Old 05-27-2015, 09:01 AM   #11
chiccogarz
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Default Re: Triumph T120 cold start after engine rebuilt

Hi all,

thanks for your help. The folllowing was the reason:
"oh right, I get it ; center adjuster is screwed down too tight and not backed off from the clutch push rod'"

It was too tight. As I have adjusted it at each kick I have compression and I can properly kick start. Many thanks to all of you
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