GT550 con rods

[tz375]

Anyone tell me the exact dimensions of a GT500 conrod?

When I say exact. One or two decimal places is sufficient (mm). "About 4 inches" is a not quite accurate enough. I'm told it's around 111mm but I need a more accurate number for something I'm working on.

Thanks

[Craig380]

Richard, this link has dimensions for the T/GT500 twin rods, is that what you're looking for?

viewtopic.php?f=2&t=8426&start=15

[old racer]

TZ i just spotted your deliberate mistake.
You title says GT550.
And your post says GT500.

[yeadon_m]

I would in any case be very interested to know the exact dimensions, especially length between centres eye to eye, of a GT550 rod!

Anyone know?

Virtual round of applause on offer

Thanks,
Mike

[tz375]

Thanks for spotting my typo. Yes I did mean GT 5 5 0 not 500. Thanks

Anyone?

[yeadon_m]

Richard,

I can tell you, the originals are a bit shorter than these: http://www.con-rod.com.tw/ktm-connectin ... -6206.html" onclick="window.open(this.href);return false;

How do I know? because they're now in my blessed 550B motor, and the pistons are poking out of the deck by ~1.5mm

I've asked the builder to darn well find out EXACTLY how much longer these are than stock....so that they can make me up the required spacers to take it back to correct at the cylinder tops.

So, IF you should learn before I do, please share! or, anyone? maybe someone somewhere has a 550 rod in their workshop. Same part number for 550 J-B, 1972-77.

Cheers,
Mike

[Suzukidave]

Maybe these guys can tell ya Richard , they list 4 in stock http://www.classicsuzukiparts.nl/2strok ... 0parts.htm" onclick="window.open(this.href);return false;

[tz375]

Richard,

I can tell you, the originals are a bit shorter than these: http://www.con-rod.com.tw/ktm-connectin ... -6206.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

How do I know? because they're now in my blessed 550B motor, and the pistons are poking out of the deck by ~1.5mm

Mike, Funny you should mention that. I am trying to work out via email with a long distance buddy what happened to his motor. In his case they fitted rods from "something else" and the pistons are around 1mm low now.

I'm going to suggest that GT550 rods must be 2mm shorter than those KTM rods which makes them 116mm. I suspect that rods in that other motor must be 115mm ctr to ctr.

All I need now is someone to confirm the actual dimensions

Dave,

Thanks I'll ask those guys.

[yeadon_m]

Richard,

Yes, please do that.

I have just also sent a message to GTReiner asking if he would kindly make that measurement as well, since he is carrying some stock of original GT550 rods. If I learn first, I'll post it up.

Cheers,
Mike

[yeadon_m]

Richard,

Just heard from Reiner in Germany. The Suzuki con rods are 117mm centre to centre. This figures, as my pistons stick out ~1mm further than I expected.

I am getting 1mm thick spacers made to put my decking where it should be. Alternatively I could fit 3 base gaskets but its probably poor practise and beeping expensive!

Cheers,
Mike

[tz375]

Thanks Mike.

So for comparison, that's

GT550 : 117mm
KTM : 118mm
RD400 : 115mm

That KTM rod is 1mm longer center to center. Your pistons should only stick out by 0.5 - 1.0mm by my calculations.

[yeadon_m]

I assumed it would be precisely 1mm at TDC, that being the extra length?
That is in line with what I'm seeing.
Was hard to be sure if just 1mm or more without knowing rid length, as I didn't know exactly where they should be.
Cheers, Mike

[old racer]

If the rod is 1mm longer centre to centre Would that not mean
when the crank is at T.D.C. the piston would be 1mm higher in the bore.

[tz375]

Correct. And if the stock rod motor has the piston 0.5mm below the top at TDC, then with a 1mm longer rod, it would be 0.5mm above the top of the barrel.

[gt-keith]

Does these different rod lengths not effect port timing ? A longer rod surely has the same effect as 'lowering' the various ports ?