GS400/500 Gr650 Hybrid engine

[Rensdw]

Eagle pass, not too far away from where you live

[Rensdw]

hello my mate; we had a 1983 gsx 400 T seize and spin the shell bearing on the counter balance shaft; this left the crankcase damaged beyond economic repair; we had nothing to lose and working on the assumption that yamaha xs twins don't have a balance shaft we tapped and plugged the balance shaft oil feed galleries and rebuilt her minus the balance shaft; she did indeed fire into life; but it was very, very short lived; she did probably 5 or 6 miles gradually developing a MASSIVE knocking from the crankshaft area before stopping permanently; after this experiment we didn't bother to strip her down again and scrapped her; we had spoken to our local suzuki garage mechanics about our plan prior to our doing it and they had correctly foretold of our dismay; and then laughed heartily at our tale of confirmation;
I hope that this little nugget of information proves to be useful; be happier than a happy thing; cheers mate Robbie

I'm sorry mate, its nothing but pure logic that the engine would fail and break down, but at least you had fun riding it to it's death haha.

I'm not planning on just removing the balancer shaft, like you know from your experience it will introduce massive imbalance.
The crankshaft has to be rebalanced because I will use different kind of pistons, with a different weight, and probably different conrods too.

the GS400X balancer shaft runs in ball bearings which are lubricated by the oil splashing up from the oil pan, no lubrication holes at all.

[hillsy]

I'm thinking about experimenting with aluminum studs, I screw them down the four inner holes and mill the ends off, now I redrill the holes again in a different place.
Of course the aluminum studs will have very fine thread to make them strong and they will have Loctite on them.
The studs holding the cylinder down will be the original studs.
This way I can skip the whole welding thing, no heat damage, no warping and no extensive machining has to be done, And in my mind, it will still be strong enough.

If this works, it will be an easy. cheap and safe method to move studs around

This might work for the inner studs but I cant see it working for the outer ones. Looking at your picture with the new stud positions, you will be left with a small crescent insert for the outer studs and I can see it pulling out quite easily.

You need to weld the holes shut and re-tap IMO. A decent welder can do this without warping the case.

[Rensdw]

This might work for the inner studs but I cant see it working for the outer ones. Looking at your picture with the new stud positions, you will be left with a small crescent insert for the outer studs and I can see it pulling out quite easily.

You need to weld the holes shut and re-tap IMO. A decent welder can do this without warping the case.

I dont have to move the outer stud holes, its such a small difference i can just use custom studs.
so only the four inner stud holes need to be moved

[hillsy]

I dont have to move the outer stud holes, its such a small difference i can just use custom studs.
so only the four inner stud holes need to be moved

How do you align the head if the studs aren't in the correct spot?

[GSX1000E]

How do you align the head if the studs aren't in the correct spot?

Offset studs locked (red loktite) into place? I too am curious as to the solution that is planned.

[Rensdw]

Offset studs locked (red loktite) into place? I too am curious as to the solution that is planned.

Instead of trying to explain this in a foreign language, I will just make it and show it to you, how does that sound?

[hillsy]

Instead of trying to explain this in a foreign language, I will just make it and show it to you, how does that sound?

By all means - please show us.

I just can't help thinking that if you are going to weld up 4 holes anyway, you might as well do 2 more and be sure it's going to work.

[Rensdw]

By all means - please show us.

I just can't help thinking that if you are going to weld up 4 holes anyway, you might as well do 2 more and be sure it's going to work.

I won't weld any of them, the outer stud holes don't have to be moved, it's only a 1mm difference so I can overcome that with offset studs.
The four inner stud holes will be moved by screwing down fine threaded aluminum plugs, then re-drill the new holes in their correct position.

[hillsy]

I won't weld any of them, the outer stud holes don't have to be moved, it's only a 1mm difference so I can overcome that with offset studs.
The four inner stud holes will be moved by screwing down fine threaded aluminum plugs, then re-drill the new holes in their correct position.

I'm not going to say that what you are planning to do will not work, but you are definitely increasing the chances of it failing by using plugs / loctite as opposed to just welding the holes shut and tapping new ones.

Remember - you are trying to create a high performance engine here. Any shortcomings in the design will make themselves known a lot quicker than with a stock engine.

[Rensdw]

I'm not going to say that what you are planning to do will not work, but you are definitely increasing the chances of it failing by using plugs / loctite as opposed to just welding the holes shut and tapping new ones.

Remember - you are trying to create a high performance engine here. Any shortcomings in the design will make themselves known a lot quicker than with a stock engine.

You are completely right, this might not be something to expirement with.
I completely forgot abouy the barrel to crankshaft alignment so i have to change my plan anyway

[GregT]

You are completely right, this might not be something to expirement with.
I completely forgot abouy the barrel to crankshaft alignment so i have to change my plan anyway

If the early 400 is the same as the later 450/500, the barrel location on the cases is by dowels at the rear of the barrel which are independent of the studs...
The same misalignment of studs is found when mixing and matching Norton twin heads. Standard fix is slot the holes they pass through and spot face a recess where the bolt head or in this case top nut goes. Use a nice thick machined washer sitting in the recess to accept the load and it's done.


Can't help thinking it would have been a lot easier using a 450/500 bottom end...the GR bits fit on nicely.

[Chuck78]

The blocks are not the same height, & I don't think a shorter custom piston would have enough pin-to-ring-land height to overcome that, so a custom CNC aluminum base gasket spacer & 2 base gaskets (see Mekanix's thread) would be the only route. & although the GR head has a far superior combustion chamber, I'm not certain the bore spacings or head stud pattern is the same, particularly the head stud pattern (ask Mekanix).

I think your best bet is either to just get a gr650, as it has a far superior frame, a great engine, & a monoshock. Or try to modify a gs450 frame to accept the taller gr engine (A LOT OF TEDIOUS/SKILLED CUSTOM WORK).

Lastly, what my weird twisted brain is compelling me todo (a whole lotta work)... I wanted to build an ultralight stripped down GS twin with upgraded brakes/shocks/fork mods wider alloy rims/battery&starter delete/rearsets/2:1/89-00 GS500E carbs& modded engine so that I could have a 325lb-ish featherlight bike that is a breeze to throw around in the hills into the tightest of turns.

I've brainstormed that the best way to do that is by using a gs400/425 bottom, 425 jugs, gs400c/425/500 cams or megacycle cams ($$$). Then determine how much overbore the aluminum blocks can take to fit in gs1000/gs500/gs1100g/etc sleeves. The problem I'm seeing is that the gs400/425 roller bearing engines have a 60mm (or some sources say 60.02mm) stroke, & the gs500 has a stroke about 4mm shorter, where the 1000/1100e/1100g have a longer stroke by about 4 or 6 mm. I think you could have the longer sleeves cut down & the ring install taper re-cut. I have heard of people resleeving their 4cyl blocks so big that in a few areas, the steel sleeve was actually showing through on the outside in the thin areas between the fins. Not sure how durable this is.

The GS850 pistons or the Wiseco GS750-844 pistons will bore right into the gs400 for a high compression 449cc engine. This & major weight reduction is the easiest route by far, but a GR650 will still be faster & more highway capable & not a whole lot heavier.
Custom 71mm Wiseco or JE pistons will make it 475cc ("should" bore into a 425 block). Resleeving to a shortened gs1000 sleeves if they bore in alright could give you up to 74mm piston capacity, but I like to try & keep it to a 3mm ovrbore for more steel to promote better heat dissipation, although the wiseco setup goes 4mm over. I'm at 3mm over on gs850 sleeves now on the 920cc & that looked pretty thin (1mm wall left on sleeves, 4mm over would mean 0.5mm wall).

The gs1000 was 70mm stock, & the 2valve gs1100g & 4valve gs1100 tscc were 72mm stock.
Going 71mm or larger pistons would yield decreasing gains due to the head (mostly just gain low end torque after that, no HP gains), so total reworking of the head (bigger valves, good porting job) is necessary, as well as GS500 carbs.

I was going to consult Rapid Ray on these, as those twins are basically half of a gs750 but with longer stroke. he mostly does tscc 4 valve per cyl bikes, but is an invaluable wealth of performance engine build knowledge. Maybe he can do all the necessary machine work all well if I were to ship the engine to Cali.

Oh, also the crank & balance shaft need to be rebalanced after going big bore on these. A 425 to 69mm may be able to get away without (little more vibrations though), but bigger big bore, probably not a good idea.

[Chuck78]

On the 77-79 crankcase/cylinders/head combo that I suggested above, I believe the displacements were as follows:

449cc - Wiseco 844cc 750 10.25:1 pistons
449cc - GS850 stock pistons (8.7:1, or mill the head and block to raise compression, then slot the cam sprockets to properly re-time the cams back to stock)
475cc - 71mm custom pistons, max overbore on GS425 sleeves
502cc - 73mm custom pistons in GS1000 sleeves bored +3mm o.s.
516cc - 74mm custom pistons in +4mm max overbore GS1000 sleeves
530cc - 75mm custom pistons in +3mm o.s. GS1100 sleeves

[Chuck78]

Ren, was searching this morning on here for "GS400 Big Bore" and came across mentions of a build thread that got deleted, but it was determined that this guy had built up the best possible combo for a bolt on. It used the 1980+ plain bearing GS450 bottom, GS500 cylinders bored +3mm over to fit GR650 pistons, and used a GR650 head. This seems to me the absolute easiest mod to do once you have tracked down the GR650 parts. Basically a bolt on. Using GS500 pistons without the GS500 head would be a step backwards, however. It is always the absolute best to use pistons that were designed for the combustion chamber, and not mixing and matching. ESPECIALLY on a very excellent modern design combustion chamber shape as the GR650's TDCC head. Twin Dome Combustion Chamber. A similar setup as the more well known TSCC. The XN85 turbo 650 four cylinder also used the TDCC chambers.



The thread on that GS450/500/GR650 hybrid got deleted years ago, but there was a youtube video of the bike running that was mentioned on an existing thread on these forums. If you have already gotten the head, you can take all kinds of measurements and make a plaster mold (or body filler, rather) of the combustion chamber, and fill out some in depth forms with all sorts of specifications and measurements, and then have JE Pistons custom make you some pistons to fit the GR650 head. The will cost you about $400 I have heard, and I am not sure if that is with rings or without.


"GS527 Beast" by youtube user hemi500:
https://www.youtube.com/watch?v=tQEVHd1cSyw

youtube user comment from our beloved franken-twin pioneer Mekanix:

Steve Mekanix
2 years ago
This is a GS450 base, GS500 cylinder and head. GR650 pistons. Bore 77 Stroke 56.6 540cc is the max you can go on a stock 500cc block @78mm. After that you can use GR650 sleeves in the 500 block and push it to a max of 570cc's @80mm. The exhaust appears to be modified at the flanges to exit at an angle instead of straight. Very nice mod."

Does anyone here have any experience with custom ceramic coatings on the pistons and cylinder head?
I'm worried about cooling, if I get my piston and head and maybe cylinder walls coated then cooling is no problem anymore.
Another benefit is that you then can ditch the oil cooler which will increase oil flow to the bearings.

BoreTech near Cincinnati, OH does piston coatings and does carbide cylinder wall embedding which makes the cylinders wear life about 400% longer