TR500 crankcase stuffer dimensions

[Gerrit]

Just curious, but does anybody have the dimensions for the crankcase stuffers used on the factory TR500, or better yet a drawing with the dimensions? I estimate from photos that the thickness is about 5 mm, but can anybody confirm this?

[tz375]

Ron Grant used to make stuffers for the GT to TR conversion, but I don't think anyone uses them anymore. Modern fat pipes seem to give more top end and more midrange that stuffed cases. IIIRC one of our racers posted on that subject before.

[Suzukidave]

http://www.ozebook.com/compendium/t500_ ... /grant.htm" onclick="window.open(this.href);return false;

[Gerrit]

Thanks for the replies, gentlemen. The tuning article doesn't mention the stuffer thickness, though- bummer! TZ, your point about modern spannies is certainly valid, but the advantages of the lighter crank still apply; the stock T500 crank is a hefty lump of steel.
Perhaps the stuffers were the same thickness as the central ridge in the crankcase casting- wonder what the function of that ridge was/is.

[Suzukidave]

I bet you could prep the cases as needed and lay a lump of clay in the case crank area and then lay in the crank . Measure the squashed clay to get a clearance and then also add a mm or so for crank flex .

[Suzukidave]

Not 500 related but looking thru the service bulletins http://www.oldjapanesebikes.com/mraxl_G ... etins.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false; i see something i didnt notice before with the GT cranks as they did the GT performance changes .. GT6 page 2 the GT crank was thinned from 28.5mm to 27.5mm . It would be interesting to weigh a 72~73 crank and then a 75~77 crank to see what the weight difference is and if the cases were left the same the case volume would have gone up a bit too .

[Gerrit]

Jörg Möller, tuner of van Veen Kreidlers, Morbidellis and others, recommended a clearance of at least 1 mm between crankshaft and crankcase, which is what I've measured on Kawasaki A7 and H1 engines, both radially and axially. Haven't checked an H2 yet but wouldn't expect it to be much different. This prevents horsepower loss due to fluid drag.
Re the later GT crank having thinner flywheels, when in the model range did this occur- with the introduction of the more highly-tuned 1975 model? The overhead guidance system reduces heat generation at the big-end so it would make sense to modify a 500 crank to the same system, whether the rods are changed to the shorter GT750's or the stock T500 length used.

[Suzukidave]

The bulletin shows May 1975 so it does look like this factory mod was done right along with the transmission change and porting changes .. i think there even was a change to the pipes maybe to draw stronger to cope with the increased case volume ? Shimming the small end does make so much more sense as the small just has to cope with the side to side rocking of the rod verse the spinning crank . And being the factory tolerances on where the bore were placed in the GT blocks shimming the small end sure would allow for the rod to not be side loaded at the crank end

[Gerrit]

With the big-end washers the piston is free to slide along the small-end bearing so I don't think that a slight bore offset will have very much negative effect. The advantages of overhead guidance are that less heat is generated at the big-end because of less friction, plus better cooling and oiling- the oil can reach the bearing more easily. Strange that few factories used this system- apart from the GT750 I can't really think of any production motorcycle that used it.

[Suzukidave]

Strange that few factories used this system- apart from the GT750 I can't really think of any production motorcycle that used it.

I suppose that shows how smart Suzuki was ( is )

[tz375]

I think it's the other way round Dave. No other factory needed to put thrust washers on the small ends and none of them has problems with overheating big ends.

It would appear that there are two possible reasons for that approach. The first is that Suzuki are not very good at making sure heads, barrels and cranks are all aligned. Any misalignment will tend to create a rubbing stress on one side of the big end on a normal arrangement.

The other possibility is that it is tied to the unusual crank design with oil slingers that Suzuki used. It is possible that they needed more clearance to get oil into the big ends with that design. Most other designs are essentially a pre-mix design in that oil is mixed in the carb or intake tract, but Suzuki pump oil directly to the main bearings and try to use a Honda 4 stroke approach to get that oil into the big ends.

I'll choose option B even though I know there manufacturing tolerances were pretty bad too.

[Suzukidave]

It does add a bit of weight to the moving parts too .. if ya hold all 6 thrust washers at one time they do weigh a bit

[Gerrit]

I wouldn't call Suzuki's crank design with oil slingers unusual. Kawasaki's Injectolube as used on the F5/F9, A7, H1 and H2 similarly directs fresh oil to one main bearing of each cylinder and from there to the big-end using oil slinger plates on the crankshaft. Strange that Kawasaki used the simpler Superlube on the smaller triples, A1 and their later street strokers KR250, KR1 and KR1-S which had a higher specific power output. The Injectolube system is much beter in my opinion, for racing too.

As for the weight of the side thrust washers, compared to the weight of even one flywheel it is negligible.

[Suzukidave]

As for the weight of the side thrust washers, compared to the weight of even one flywheel it is negligible.

i was thinking more about added weight to the piston assembly .