GS400t with 4 valve cyl head

[mikestp]

I have a rareish GS400 bike here. it is a Canadian model and is 400 cc 1981. In Canada, they sold the 400 CC model for a few years different from the USA that went to 425 cc then to 450 cc. The rarity of this bike is that it is a 4 valve piston cyl head combo rather than the more common 2 valve head. I am in need if a std piston to replace one that has a broken ring land. Anyone here know of one that might be available? and failing that can I replace the cyl head with a 2 valve and a pair of pistons that match? Has anyone got a pair of two valve pistons and cyl head with all attachments? (such as cams, valve cover, chrome end caps?) and anything else you might think I need? Thanks in advance for any help you might offer.

 

[Guest]

As well as the piston, you'll need a head gasket which is particular to that motor; the base gasket is the same [I think] as a US 450. Rings may be scarce as well. I think ones from a Yamaha XT225 may??? fit. Suzuki Canada still has some things, and cmsnl.com has reasonable inventory.

The whole US 450 top end will fit the 400 block. I'm running one. This solves a lot of parts problems.

 

[mikestp]

Well if your reply is as I see it. A 450 cylinder, a pair of 450 pistons, and all the misc parts that go on the head will fit the crankcase of the 400? Or are you saying the 450 head will bolt to the 400 barrel and if I also replace both pistons with the 400 two valve type all will be fine? That might be the easiest route for this.

 

[GregT]

Rest of the world it's a GSX400. The heads eventually crack from the exhaust valve seats to the plug holes so if you are planning on keeping it, the 2 valve top end is a good option. You will lose some performance though.

 

[Guest]

Rest of the world it's a GSX400. The heads eventually crack from the exhaust valve seats to the plug holes so if you are planning on keeping it, the 2 valve top end is a good option. You will lose some performance though.

Depends on how you define performance. The 4 valve head is rather compromised by the port angle so for peak power it's pretty much a standoff; for torque in especially the 4000 to 7000 range the 450 wins easily, maybe because it sucks the carbs open sooner. On the street the 450 is a better motor and the cooling 'system' - fins - are conspicuous by their near absence on the 4 valve. IOW, the rocker boxes ate the cooling fins.

There's just something about hemis....but @10,000 rpm the 4 valve is pretty intense.

 

[Guest]

Well if your reply is as I see it. A 450 cylinder, a pair of 450 pistons, and all the misc parts that go on the head will fit the crankcase of the 400? Or are you saying the 450 head will bolt to the 400 barrel and if I also replace both pistons with the 400 two valve type all will be fine? That might be the easiest route for this.

The barrel is different. Bigger bore - 71mm? You need the front chain guide and the rear guide is different too, but the 400 will work but you may have to make a spacer to move the cam chain tensioner out about 3mm or so. Carb boots are different; exhaust bolts right up.

 

[mikestp]

I am attempting to buy a 4 valve piston, it will make it easier to repair knowing what parts fit. At this time I am not certain of what will or will not fit. The 400GSX barrels are not measurably worn, and all I need is a replacement piston. I am not sure a 450 barrel will fit onto the crankcase. I found piston replacement candidate here:
https://www.ebay.com/itm/PISTON-GSX...=gsx400+piston&_from=R40&rt=nc&LH_TitleDesc=0

The ebay advert says it is for a 1983. I can hope it will match the other piston i have. the bore size is 67mm, same as my bikes bore size. My head gasket was a good removal and with copper spray I can reuse it. I hope this ebay advert for a 4 valve piston is te correct one

 

[TxGSrider]

Just out of curiousity , what caused the ring land on your old piston to break? It'd not a very common issue on most engines I've seen outside of ring gap issues and such.

 

[Gorminrider]

Be Very Careful. That part number does not match as for a GSX 400. a TWIN .Goto parts suzuki motorcycle accessories spares replacement aftermarket

BUT a google search for "suzuki 12111-33300" comes up as possibly for a GSX 400F which is a FOUR CYLINDER bike

 

[mikestp]

Be Very Careful. That part number does not match as for a GSX 400. a TWIN .Goto parts suzuki motorcycle accessories spares replacement aftermarket

BUT a google search for "suzuki 12111-33300" comes up as possibly for a GSX 400F which is a FOUR CYLINDER bike

https://www.bikez.com/motorcycles/suzuki_gsx_400_e_1981.php
This shows it is a twin... and 67 mm in size.....

And this 1983 shows as a twin also 67 mm in size
https://www.bikez.com/motorcycles/suzuki_gsx_400_e_1983.php

 

[Gorminrider]

re-read my post?
an F is not the same bike as an E

there's an "F" on homepage this monthhttp://www.thegsresources.com/

 

[mikestp]

ahhhh placng an underscore under in message under the letter F makes it look like an E. My error, I would have asked to have the piston in question measured to see if t was 67 mm

 

[Gorminrider]

yes it's not very plain with the line under it!... But main thing is, don't have the wrong part showing up!

 

[mikestp]

broken land

broken land

here s a pic of the broken piston

 

[Gorminrider]

nice picture of disaster! Lots of these bikes in Canada, you know, but just tearing it down to get the piston is a lot of work...you might want to get the whole engine as scrap cheaper if there's a boneyard near you.

 

[mikestp]

one hour to pull apart 3 hours to reassemble .....

 

[mikestp]

Ok to keep this posting up to date. I was able to find a new piston for this bike in Singapore. And the gaskets from Japan. There are very few parts that are interchangeable with the two valve model. the cylinder head bolts are a different spacing, the gaskets are all different, the rings are different, the head gaskets are different as are the base gaskets. in fact, in my opinion, the only thing that might interchange is the spark plugs. So if you are considering repairing a 4 valve, either search the net for the proper parts or swap out the complete engine with a two-valve engine.

 

[Guest]

The head bolts are only different spacing on the roller crank 400 '77 - 79. I think the 450 base gaskets are the same; everything above that IS different but bolts directly on. Below the beltline they are identical, except for the rear camchain guide, which works anyway.

A two valve 400 is very different, and could be a challenge to get into the newer frame. Hard to imagine why you would want to, unless you already had a nice one looking for a new home. The two valve 450 top end drops right on the four valve. Exhaust fits, carbs fit, but intake boots are different.

Glad to hear you found a piston; I had some well used ones but gave them away along with the rest of the plot this Spring. Considering the cost of gaskets and such, you're better off with a new one anyway.

I disagree; you don't have to swap the whole engine. Used 450 engines worth buying are usually twice the price of just the top end, plus you get to inspect everything and use new gaskets etc. OTOH to plug and play a used engine is quick, if it works out; in many cases you end up undoing the top end of the 'new' used one anyway.

 

[mikestp]

The head bolts are only different spacing on the roller crank 400 '77 - 79. I think the 450 base gaskets are the same; everything above that IS different but bolts directly on. Below the beltline they are identical, except for the rear camchain guide, which works anyway.



A two valve 400 is very different, and could be a challenge to get into the newer frame. Hard to imagine why you would want to, unless you already had a nice one looking for a new home. The two valve 450 top end drops right on the four valve. Exhaust fits, carbs fit, but intake boots are different.



Glad to hear you found a piston; I had some well used ones but gave them away along with the rest of the plot this Spring. Considering the cost of gaskets and such, you're better off with a new one anyway.

I disagree; you don't have to swap the whole engine. Used 450 engines worth buying are usually twice the price of just the top end, plus you get to inspect everything and use new gaskets etc. OTOH to plug and play a used engine is quick, if it works out; in many cases you end up undoing the top end of the 'new' used one anyway.

Base gaskets are different the head bolt stud spacing is about .100 off from the holes in the base gasket. The head gasket is the same problem. The bore is a different size, The rings, of course, are different I do not know if the crankshaft is different but since the other major parts are NOT interchangeable it would be fruitless to even bother to look. In other words, there are perhaps a few interchangeable parts..... spark plugs, hmmmmm im running out.... No way will any parts from a 2 valve 400 era 1982 fit a 4 valve 1982.

In the USA, there are no 400 4 valve engines since they were never sold in the USA. only Canada and Europe and Japan had em.

The xhaust does indeed fit onto the two valve head. But since you cannot fit a 2 valve head onto the cylinder of a 4 valve engine... why would anyone care.

I think you did not read the entire thread to find out I have a 4 valve GSX400E I needed a piston and after 4 weeks i found one in Singapore. Gaskets were found in Japan. Bike being reassembled now. I just wanted to update the thread in the hopes that anyone else looking for parts for a 1982 GSX400E should not waste any time looking in the USA for such parts. I started the thread with the possible swapping of some parts from the 2 valve engine. But alas no parts interchange. It might be possible to swap out the 4 valve engine for a USA 2 valve engine either a 400 or 450, but I am not sure of the engine mountings.

 

[Gorminrider]

John, what do you think are specific differences between camchain guides gsx 400 to gs 450? part numbers are very close ...gsx400=128-44250 versus gs450=128-44150.

I'm looking at one here from a gsx400 that needs replacing. ... the one from my spare engine torn down is a lot better to look at but is showing tiny cracks in the plastic..... I'm not too happy to go through the trouble if the replacement is no better while a new one for a 450 seems easier to get...(59.00 US!)