Yamaha DT175 no start

[newrider3]

I'm trying to get my '80 Yamaha DT175 two stroke running to get it registered and start riding around town, but I'm getting no fire at all. This was a running bike before I rebuilt it.

Compression is excellent, in fact it has new crank seals, new rings and hone, and the head has been lapped.
Excellent spark, the coil and stator were replaced a while ago to cure a hot no-start situation, brand new NGK plug. I pulled the side cover and checked the timing, and everything is spot on, flywheel key is intact.
Fuel is fresh, carb is spotless internally, reeds are in great shape, intake has been re gasketed and sealed.
It's getting plenty of fuel, but I don't even get a pop out of it. No response to priming the cylinder or spraying a little carb cleaner. It doesn't even try to fire if I attempt to push start it.

I'm really stumped with this one. There's nothing preventing the bike from starting, but it doesn't even fire. Any ideas?

 

[Bluethunder3320]

i had the same exact thing happen to me with my yz125, i did a complete rebuild, and no fire.. i was getting really pissed off since i had put hundreds of dollars in it and lots of work.

this might sound pretty stupid but here's what i did. flipped it upside down, unscrewed spark plug and turned it over,, and out came a lot of assembly oil and gas. turned it right side up, and it fired up on the first kick!

 

[newrider3]

You'd think I would get a bunch of crap spraying out of the plug hole any time I kick it without the plug if that was the case...

 

[crazyman]

Is that a dual plug cylinder head like the dt250? If so, try the other hole. I had that problem once.

 

[newrider3]

Nope, single plug.

 

[Bluethunder3320]

i tried cranking my bike over upright with the plug removed and nothing came out. all the gas/oil was sitting in the crank case and it only came out when i flipped it over. if you've been using starter fluid and priming it chances are its just flooded

 

[crazyman]

Have you tried the hardly ever fails trick of getting the plug's tip hot with a torch, installing it, and attempting to start with a hot plug?

(A propane torch is sufficient)

 

[newrider3]

I just went out and turned the bike over and cranked it, not a drop of anything out of the cylinder.
I've never heard of the hot plug thing, all I have up here is a pencil torch so I might give that a try and see.

 

[DS13]

Have you tried the hardly ever fails trick of getting the plug's tip hot with a torch, installing it, and attempting to start with a hot plug?

(A propane torch is sufficient)

I did that to my kx 125 turned over within a few kicks... ya have to get the plug pretty hot though, no 3 second warming.

 

[newrider3]

Just tried it, got it warm enough the electrode tip was discoloring, nothing.

 

[DS13]

Does it still spark?

 

[B man]

well theres gotta be a spark issue. check and make sure nothing is grounded out.

 

[newrider3]

There's plenty of spark with either the plug out of the cylinder, or a second plug hooked up out of the cylinder. What would cause me to lose spark with the plug in?

 

[zbuck]

A plug will fire when grounded out of the engine. But not when installed in the engine under compression. Try a new plug.

 

[cumminsbayou4x4]

could it be the reeds what do they look like?

 

[newrider3]

I've tried two brand new plugs, and already checked the reeds, they're nice and springy and seal properly.

 

[cumminsbayou4x4]

idk what it is then sell the motor on ebay saying its is a rebuilt motor

 

[DS13]

I bet your engine is flooded. Try leaving your spark plug out over night

 

[kendelrk]

when rebuilding it/tearing the motor out im sure you disconnected the electrics, if you can take off all the wires to the kill switch, do it and then try, you may have switched two ground wires around or something.

 

[newrider3]

I already turned the entire bike over and cranked it, nothing came out of the cylinder.
There is no stock wiring left on the bike, I re-wired it myself and have had it running before. I know for a fact neither kill is engaged, and I have even tried kicking it with the kill lead completely disconnected from the coil. The last thing I can think of at this point is a new ignition coil, if this one is giving spark it may still be too weak.