Snowmobile Fanatics banner

1 - 12 of 12 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
I am new to this forum but I am excited about having somebody actually be able to answer my questions.

Essentially what I have is an older Yami 340 that had a bent crankshaft (terrible vibration). The engine had been rebuilt and he must have dropped it or something. So this guy parked it and gave up. He decided to give it to me, and like a moron I thought that another broken Yamaha would look good in my field. I had another enticer with a 400 and a dead piston, so I decided to use the top end of the 340 and install it on the 400 crank. I was wondering why it clangs so badly now, and also how would a fellow go about removing the connecting rods from the crank? It seems to run good for now aside from the awful racket and a constant worry that the sled will give out at the worst possible time. (40 below weather 40 miles in the backcountry). I appreciate the advice, admonitions etc.

Yamaha Blues
 

·
Registered
Joined
·
127 Posts
One reason for all the noise in the engine may be the 400 has a longer stroke than the 340 causing the pistons to slap the heads. Other possibilities could be worn piston rings, worn out crank bearings or connecting rods. The bearings on the crankshaft are normally pressed on so you'll need a press or heavy duty flywheel puller and torch to heat up the bearings to pull it apart. I would probably look for a good running used 340 engine to put in the sled. It's more valuable original.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3
Thanks, I kind of thought it was the con rod bearings being a lot more worn out than the new pistons in the 340 upper end. I put the two together thinking that they would work and I would not be out any money since they were both pretty dead anyway.

It was just a dream that I would get away with it, I guess one can only pull the wool over the snowmobile gods eyes only so many times.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #4
If I take the connecting rods off of one crank, would I be able to put them on the other crank, I am thinking not but... Also, how do I tell if the oiler is working, they are a little different on the 340 and the 400's I am assuming they work by vacuum from increased RPM and are connected to the throttle to increase flow when the throttle is opened. I worry that that is why the 400 went out in the first place. So i was thinking that it was clanging because of lack of oil.

thanks
 

·
Registered
Joined
·
127 Posts
Hi there,
One way to test if the oil injection is working is to pull off the oil lines going to the intake manifold. Then start the sled and see if oil is pumping through the line. you may also want to run a 40:1 premix just to make sure the engine gets lubricated. In the last few years I purchased an 80 Yamaha Exciter 440 and an 82 Yamaha SS 440. I plugged the oil injection lines and just ran premix and glad I did. The second time our kids used the Exciter the oil injection pump blew apart and if it wasn't running premix the engine would have blown. Just an idea if you want to be safe with the older engine. Before taking the engine apart again try the premix and see how it works.
John
 

·
Registered
Joined
·
510 Posts
i dont think there is even such thing as a 400 enticer. plus 340's and 440's use different top and bottom ends. thats how all there 340 and 440 fan free air and liquid motors are and have been. stroke is usually the same though.
 

·
Registered
Joined
·
127 Posts
Believe it or not there was an Enticer 400 made in 89-90. It was called an Enticer 400 LT. I think I remember seeing it in an old Snowmobile magazine. They were a utility sled like the Bravo long-tracks.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #8
Yeah, I have two of those 400's actually 399's they have the CID stamped on the cylinder chambers.I think they were the sleds that yellowstone Park used for a awhile so they are all over Montana. I think I will try the mix, I did pull the oilers off but no oil seemed to come out, that is why I figured it might need vacuum pressure. It makes sense now.

Thanks guys
 

·
Registered
Joined
·
2,505 Posts
Did you change the pistons too?
remember different cylinder bore.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #11
The pistons were brand new and the cylinders were new, they did not even have any carbon built up because it was undrivable with the vibrating crankshaft. I probably should not have done it but, I took the old crankshaft of an old 400 and used that to run the new 340 pistons and cylinder heads, I think my biggest problem is a fairly worn crank running a new set of pistons. They seemed to fit pretty well and I have driven it, but not with a premix yet. I think the reason that the it clangs is the bad oiler is not lubricating the engine. Before I assembled it, the rods seemed good enough to use. I am going to run premix and ignore it, if it blows oh well, I'll just buy an engine. I just wanted to avoid spending money because, well I really don't have much to spend.

Anybody know where I might be able to find an engine in the future, or maybe just a new crankshaft, and seals. My local Yamaha dealer is not helpful, plus these old yami parts I think are getting absolete.

Thanks

Ted
 
1 - 12 of 12 Posts
Top