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1982-3 Yamaha 400 doesnt start..

8956 Views 20 Replies 7 Participants Last post by  yamatrike400
A few years ago i picked up a 1982-3 yamaha 400 for 150$ that i welded a ATC axle on the back to make it a 3 wheeler for offroading.I was mudding with it and i revved it up to like 12k rpm and dropped the clutch to get out of a mudhole and it broke the 1st gear into pieces.This was after about a year of abuse.I finally put the tranny back together in it,i also replaced carb bowl gasket,needle,and seat.(54$ ouch) but now she wont fire up,all it does is blow flames out the exhaust once in a while(tried with exhaust on and off) i did not mess with valves,timing,nothing.any ideas?She ran WONDERFUL before i tore into the tranny.
It has great spark on both plugs(plugs are new)and when i have the right coil wire on the right plug and the left on left plug,the engine blows out flames with more of i light poof sounds,when i have the wires opposite,the engine actually sounds like it fires but only once in a while and also backfires out carbs.ALSO, when the wires are right coil to right plug left to left,when turning over,the engine will momentarily stall like it gets a massive amount of compression..

If anyone could help it would be awesome i really miss this thing.Heres a pic

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Oh yeah shes fun, its amazing how good she did in the mud having that skinny front tire.Ya just gotta keep the front end up :-D

As far as i know it did not skip because it ran fine before i took it apart.Everything checked out fine before i put it back together not much damage at all.Also has 130 lbs compression in each cyl.
Anyone? I would love to get this thing goin again.
To get into the tranny you had to pull the engine completely apart right? Better check to make sure that your camshaft and ignition timing was put back together properly. Then do a compression check. I sincerely hope you have a manual. If you put the camshafts in wrong you may have bent some valves. If you didn't align the ignition pickups properly it'll never run.
I just split the bottom half, didnt have to mess with upper end of engine,ALL i did was replace the gears.There is only one way to mount the stator plate,so it must be right.And yes i have a manual.This is really stumping me.

And alot of people have said things about mounting a gun on there ahahah

And no, the mudholes in my back yard :D
Guess what??? I got her goin.It turns out i put the plate backwards that mounts on the the crankshaft that touches each breaker thing as it goes around.TO SAY THE LEAST I AM VERY HAPPY.Very simple fix.Thanks guys.
Ok, so i got it all ready to go and drive it,but i realized when i unhooked the battery(from a car) that the engine would shut off.It didnt used to do that,any idea on what could be wrong there? i was drvin it around with a big car battery ratchet strapped to the back :D

The 400 trike has long since died. It really went through hell.

Anyway, i got the dreaded Yamaha 490. Its an IT, though. Got it for 100 bucks and it ran real good and was fast as hell. As much as i hate the vibration and weight,I love the thing, nothin like wheelies through every gear.. I wore snowmobiling gloves while riding it, the vibration is a killer. I melted the piston on it going WOT down a dirt road...the thing locked up going 80+ and almost made me eat dirt. I also acquired a 85' IT200 for 50 bucks. The things a little screamer. Here's some pics.
The 490 monster

When i got the 200,

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Where are you finding these cool deals? I'd take that 490 off your hands if you weren't in MN.
I was talking to a guy about dirtbike's and stuff and he said he had a old 490 sitting in his garage, it has been for years. And the 200 my neighbors dad had, i jokingly offered him 50 bucks for it and he dropped it off a few days later. It just needed a spark plug! I don't think i'd sell the 490...I need a fast bike. :D
Yup i've seen your article. very nice. I'm going to be doing this head mod.
Yz 490 tips and tricks and the head mod diagram

Mine melted the piston because i was too lazy to buy a new air filter for it...And yeah i don't care what the 490 haters say, i love the thing. Simplicity, Power, Speed.
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