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77 TT500 Won't Start?

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My 77 tt500 yahmaha won't start, redid the points, valves, rockers, gears, etc, won't even backfire now, I'm stumped. Any advice.

 

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Like my dad used to tell me back in the 70's,  All it takes is gas, spark, and compression.  Is there spark at the plug? Is the plug getting wet?

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Like my dad used to tell me back in the 70's,  All it takes is gas, spark, and compression.  Is there spark at the plug? Is the plug getting wet?

There's spark, and compression, and the plug is brand new but yes it's getting wet

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Is your spark nice and blue, or dull yellow?  What is your point gap?

So what I discovered later that my dad failed to mention was you also needed correct spark timing and cam timing.  Did you redo anything that affects valve timing?

 

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Is your spark nice and blue, or dull yellow?  What is your point gap?
So what I discovered later that my dad failed to mention was you also needed correct spark timing and cam timing.  Did you redo anything that affects valve timing?
 

I'll have to check the spark again, but it's gaped by the shop manual, and we didn't mess with the valve timing.

Cam and spark timing is good

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OK. Is it a new condensor?  I have seen where an open condenser would let you get the first sprak out but not a whole train in a row.

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I'll have to check the spark again, but it's gaped by the shop manual, and we didn't mess with the valve timing.

Cam and spark timing is good

It's not super old, maybe 4 years old at most, we ran the last one for almost 20 years and it still works.

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Try this trick. While the points are closed, spring them open and put a clean white thick piece of paper like a business card between the contacts, put some pressure on them against the paper and pull the paper out. Do this a few times it seems to help new or freshly filed points make good contact.

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Try this trick. While the points are closed, spring them open and put a clean white thick piece of paper like a business card between the contacts, put some pressure on them against the paper and pull the paper out. Do this a few times it seems to help new or freshly filed points make good contact.

I'll give it a try in a while thx

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I don't recomment this but on my old Maico I used to stick a screwdriver up in the spark plug boot and touch the shaft and jug at the same time with my hand and turn the motor over.  If the spark kicked the crap out of me I knew it was fine. If it just sort of thumped me I knew it was the problem.

Assuming good spark, if it were me, I would look into the carb next since gum resin tarnish and varnish in fuel is the number 1 cause of all no start problems.

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I don't recomment this but on my old Maico I used to stick a screwdriver up in the spark plug boot and touch the shaft and jug at the same time with my hand and turn the motor over.  If the spark kicked the crap out of me I knew it was fine. If it just sort of thumped me I knew it was the problem.
Assuming good spark, if it were me, I would look into the carb next since gum resin tarnish and varnish in fuel is the number 1 cause of all no start problems.

It has good spark so I'll look in to the carb

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I am heading to the shop to do some work on mine, and for later netflix just sent me Resident Evil: The Final Chapter dvd.

Good Luck and Keep us posted. 

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I don't recomment this but on my old Maico I used to stick a screwdriver up in the spark plug boot and touch the shaft and jug at the same time with my hand and turn the motor over.  If the spark kicked the crap out of me I knew it was fine. If it just sort of thumped me I knew it was the problem.
Assuming good spark, if it were me, I would look into the carb next since gum resin tarnish and varnish in fuel is the number 1 cause of all no start problems.

Carb is good and clean

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Is your points gap set correctly ? .014 isnt it ?

flywheel spinning ok - no sheared woodruff key ?

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Is your points gap set correctly ? .014 isnt it ?
flywheel spinning ok - no sheared woodruff key ?

Yep gaped good, fly wheel ok
I'm super stumped

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Pilot jet.  You may think the carb is clean but the pilot jet is probably clogged up.

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Like the previous poster said, spark, fuel, compression, and timing are "all" that is required to make an engine run.

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2 hours ago, Octane said:


Carb is good and clean

I used my little brother as a spark detector.  It worked once!

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Wait a minute, points?  Is the plate that the points mount to lined up on the timing marks correctly?  I had this come loose on my XL250 once and it bedeviled me.

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Wait a minute, points?  Is the plate that the points mount to lined up on the timing marks correctly?  I had this come loose on my XL250 once and it bedeviled me.

Yes they are linked up

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