400, 425, 450? Which one is the best? Why?

[Roger P.]

I have read that the 425 was the torquiest of them, but if I was getting one, it would be one of the Katana styled 400's, or the last 400S in black and red. Maybe this was only available in Canada, I don't know.

Anti-dive on one fork leg, that must have really helped eh? It's odd that on the Suzukicycles website, almost all of the early twins were described as 8 valve engines in the summary.

[Nessism]

Suzuki's 4 valve/cylinder heads were/are good, but TSCC is just a marketing gimmick.

[CR_GS_450]

I truly enjoy my slightly modified L version, but it doesn't resemble an L which is why I like it, haha. If I had to pick I would buy a 1980 450 SX, gorgeous bikes and I love this motor. But I have a feeling I won't get rid of my 86 for many years to come, with 38k hard riden miles on the motor though I smell a rebuild in the near future.

[pete]

Rebuild soon? Nah, she'll be right! Mine has 96k km's (not miles) on the clock and everything so far internally still measures within tolerance.

Do the valves and stuff and leave it at that... if it ain't broke don't fix it

[CR_GS_450]

I have a decent piston slap and some other noises that have started to emerge, as well I would like to do a custom piston kit so that she will behave with these CR carbs. Also, I have a slight oil leak I would like to take care of...We shall see.

[pete]

Aaaah ok, sounds like there's a reason then

[salty_monk]

I was toying with the idea of building something like this... http://www.rycamotors.com

Problem is that I'd have to lose one of my other bikes to do it

[BentRod]

I will get back to you guys about the reliability of the gs400 engine. it can be broken. I have rebuilt two of them now. the pictures that will follow are not for the faint of heart...

[BentRod]

we will start easy. I want to state that I always kept my bikes well tuned and timed by either myself or my mechanic. I buy my bikes and engines used, so I cannot speak the to treatment and care given by PO

Valve wear. both of these are intake valves.Both came out of the first engine i rebuilt, and the left one is still in usable condition. the one on the right has been badly scorched. remember this is an intake valve. you can see the ring of badly burned metal where the flow of hot gas went from laminar flow to turbulent just above the valve head.



next, pitted piston. this came from my second engine. I was running lean to get a little more power. Also the extra hot engine heats up the tank quite a bit and helps with the chilly spring morning ride to work. These marks are the result of the heat burning through the carbon layer, and hitting the aluminum. when the heat breaks through the carbon the material is to hot that when it hits the aluminum a bit of metal instantly melts, and spits off. The pitting eventually caused pre-ignition and knocking.



Smacked valves. the evidence can be seen by the marks on the intake side of this piston. Also notice the damage around the edges. This piston came from my first engine.



Better view from the side shows the extent of the damage, and burn marks down the side are evidence of blow by of burning gas past the piston rings. burning off the oil this would have removed any protection for the cylinder walls, now being scored by the damaged piston.

[SVSooke]

True to what I think are the best small Suzi's I bought my wife one of these for her first bike

85 or6 GS400,think it's a 86 with a build date of 10/85.

[BentRod]

now the really scary stuff

This is the exhaust cam from my first destroyed engine. the came shaft went halfway through a corner on the highway. bits and pieces of tappet and rocker went down the engine into the gears and locked up my rear wheel. the rear started bouncing like mad. I hit the front brakes hard and brought it over to the side of the road. once i got close to the guard rail i just jumped off, still doing almost 40km/h. I hit the down hill slope of the ditch and tumbled. ATGATT, so I came out of it ok. the bike had kept rolling down the shoulder and came to a stop leaning against the guard rail, pretty busted up but upright.







note the extensive cam wear. The rocker and the cam were worn well past tolerence. the rocker snapped off and jammed the cam shaft, breaking it.

one more note on the piston heads from earlier. Take a look at the shap of the hole that the wrist pins go in. the burnt one isn't right.


and this is the wrist pin that came out of it

note the melted center. this pin was welded to the connecting rod.