Need info about 225dx trike!!!

[mike11743]

I know it's not a blaster, but at least it's still a yamaha. Anyways, I bought a 1984 225dx on impulse for $180. It's in decent shape and almost everything is there it looks like. It does have a broken valve though, or at least according to the guy I bought it off of. I know it's shaft driven, but thats about it. I know someone has experience with these. Basically i'm looking for any info, common problems, and i'm sure ill have questions as I go along. What would cause a valve to break. I know the guy i bought it off of said that he bought it with a bad valve, put a new valve and valve guide in and had it idling for like 10 mins before it broke again. He said he had no idea that he had to set the timing, so could this have broken it? I would think it wouldn't run if he didnt set the timing correctly

 

[Caterpillarmech]

Yes! If he had the timing off or if the valve lash was too tight it could break it in theory.

 

[YFS101]

yeah I had a couple of them... great bikes

if the engine was rebuilt first things I would look at are

is the piston in backwards?
is the cam timing correct ?
Is the cam damaged ?


its common for guys to set the timing off by 180 degrees and that will cause the same problem your having.
fix the valve/seat/guide if needed, check that the piston is installed correctly and put it back together properly. Make sure you set the valave clearance properly.
Its well worth what you paid for it.

 

[Braaaptor]

yeah I had a couple of them... great bikes

if the engine was rebuilt first things I would look at are

is the piston in backwards?
is the cam timing correct ?
Is the cam damaged ?


its common for guys to set the timing off by 180 degrees and that will cause the same problem your having.
fix the valve/seat/guide if needed, check that the piston is installed correctly and put it back together properly. Make sure you set the valave clearance properly.
Its well worth what you paid for it.

^^Agreed! I like these old Yamaha 4-pokes, and they're easy enough to work on and last forever. Valve lash is .003-.004" for the intake, and .004"-.005" for the exhaust.

YFS101 is right. Be sure both valves are closed when setting the clearance. I'd pull the cylinder head off the engine, check what was mentioned above, and re-assemble it carefully. A valve won't just break; something has to be wrong for one to snap.

When you go to time the valves, there is a plug on top of the flywheel cover that you must take out. You'll see a pointer cast into the cover, and a 'T' mark on the flywheel. Line these two marks up. Now, take the cam gear cover off the side of the cylinder head. There is a pointer cast into the top of the head, and a tick mark on the cam drive sprocket. These marks must also line up for the valves to be in time. If not, there's your problem! Check the valve timing before pulling the engine apart to see if the last guy who worked on it got the valve timing set correctly. Chances are, he didn't.

 

[4cfed]

known for trans problem, i hav e abuddy with a nice one that wont go into gear and no one wants it, runs like a top just junk trans,,

 

[MXsandracer]

great price. they're tanks, go through alot and easy to wheelie.

only issue i ever had with mine was that the strap that holds the battery in place rotted and broke, i didnt notice it was rubbing against the tire and ruined the battery

 

[mike11743]

okay. I got this thing torn apart, at least got the head off. The intake valve doesn't completely shut. It does move as i move the cam, but just does not shut all the way. Anyways it took a very small knick out of the top of the brand new piston this thing has in it. The knick is probably 2 or 3 millimeters deep and the piston is probably about 3/4 of an inch think there. I don't think I would re-use it, but what are your guys' opinions?

Another question I have is as im'm testing stuff out to see if it's worth rebuilding, I have the head off so that I can turn it over easily to see if I have spark. When I put it into gear and pull the pull starter, should it move the whole bike say like a blaster would. I don't exactly know how the clutch on this thing works

Another one: Any way to tell if the tranny is any good. Like a more in depth look than just checking the fluids?

and finally for anyone that has one of these, right behind the right side footpeg is a bar that looks like something mounts to it. A blaster footbrake fits on it perfectly, but hits the footpeg if i try to mount it so it would be useable. What goes here?

 

[mike11743]

okay so I got this head all apart, and the first thing that I noticed is that the valve that is in there is not broken. This is the exhaust valve that this kid replaced. The valve seems to have a lot less resistance than the intake valve when spinning the cam with a wrench, but it does fully close. Is this normal? Also when taking out the camshaft, I noticed a decent amount of up and down play. I traced it to the outside mounting collar (the aluminum piece that that slides over the cam and into the head). Could this have caused my problems?