Triumphrat

sLoRide

I bought a 73' Tiger 750 a couple months ago. I've been tinkering with it -cleaning the carb, changed fuel lines, flushed the tank, and other minor tune-ups. but I have some problems...

My carb setup is a single Amal concentric carb with a 260 main jet.

Problems/Questions:
1. My plugs are char black (running too rich), Is my main jet too large? should I have a 240?

2. I start the bike with the choke lever in the down position, I think this is the off position because the choke slide located inside the throttle slide is all the way up when the lever is down. -Is this the correct setup for the choke to work? It looks like someone has messed with the cable.

3. After the bike runs for a while or if I go for a short ride down the drive, the engine side of the throttle slide has black/brown sticky stuff on it, and if it continues to build up it makes the throttle slide stick. Do my valves need to be adjusted? It seems like unburned fuel is escaping the cylinder and coming back out the intake...any thoughts?

Thanks for any kind of help...I need it.

bum

If it's like a Mikuni the choke is off when the lever is up. (the plunger is down)

bum

Sorry sloride. I didn't realize you were talking about the lever on the handlebars. My mistake.

thirdbike

Your manual calls for a 280 main with a 106 needle jet. These and the needle may be badly worn causing the rich mixture
Your choke is on when the choke slides are down inside the carb throat blocking the airflow so as to enrich the mixture.
The cable holds the choke open for normal running.
If you have fuel/exhaust residue deposits in the carb, your bije cannot be running too well if at all. Your valve timing may be off but unlikely. It may be that you are in dire need of a valve job.
To prevent further damage, you probably shouldn't be running the bike with these reported conditions

tangomike

I too have a 73 750 Tiger single carb and have been stuggling with it. My advise is to buy a new .106 needle jet, a new needle, and even a new needle clip. These are the three things that helped me the most. I would also make sure the float level is set to around .080. Also what size slide do you have. Mine is a 3-1/2.
On the choke level you can determine the setting but opening the throttle a little(motor off) and stick you finger in the carb. Now work the choke lever back and forth and see which way it goes.
From your description of the throttle slide being black, and you plugs charred, I surely need a new needle jet if nothing else.

TangoMike

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sLoRide

Thanks for the feedback, I think I will go with ordering the new needle and jets, and while I'm waiting for them to show I can pop the top and check the valves. -Any suggestions as to where to buy carb parts?

sLoRide

I just finished reading another thread about a bike backfiring through the carb, indicating that the timing is too advanced. Mine doesn't backfire through the carb frequently, but it has a couple times while I was tuning (or trying to) the carb. - any thoughts?

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tangomike

Thoughts? The scientist in me thinks like this. A pop or backfire thru the carb is an obvious indication that fuel has ignited outside the cylinder chamber. With that in mind, how does it happen? Timing, period. Fuel cannot ignite outside the cylinder chamber if the "timing" is correct. But that does not me the timing is out. (What did he just say??) Another way the timing(of the fuel iginiting) retards ever so slightly, is the delay of fuel ignition. This is common to all internal combustion engines, not just old Triumphs. It is the same principle as the physical timing being off. The fuel does not ignite or does not ignite completely until the exhaust valve is closed and the intake valve is open or partly open. If you get a little pop or backfire thru the carb while tuning, this is very normal. My advise is to CHECK the timing, but don't get too hung up on it, just make sure it is right. Your real problem may just be only a worm needle jet. The jet is brass and the needle is stainless steel so the jet wear out first.

My thoughts.

TangoMike

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sLoRide

Thanks, Tango
As a general rule of mine I like to try the simplest solutions first, so I will definatly be ordering a needle and jets. If this dosen't do the trick, my next suspiscion is my plugs need to be hotter (this is also suggested by the manual), any thoughts on this (makes me feel all scientific now. ha)

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tangomike

You did not mention what type ignition do you have?? Stock?? Mine is a Boyer.

TangoMike

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