T500 with different intake port configurations

CaptCatFish

After finally getting all the fuel and air intake gaskets and boots necessary for my 1972 T500 resto project, I've discovered that the intake ports on the cylinders are different and probably the result of some half-ass rebuild attempt by the previous owners.

The left side has a bridge in the intake port that is identical to the bridge on both cylinders of my spare donor motor. The right side has a bridge in the intake port that extends from where it makes contact with the piston to flush with the carb intake boot.

I have had the bike running but had difficulty dialing it in which I attributed to cracks in the rubber intake boots for the carbs and air cleaner. I'm now concerned that the engine may be impossible to dial in with such a major difference in the intake port configuration.

Is it time for a proper overbore using cylinders with matching intake port configurations or am I making a mountain out of a mole hill?

Many thanks to the experts here. I don't know what I'd do without you.

Jim

dorT500 · Posted: Sat Jul 17, 2010 5:18 pm Post subject:

Got Pics? I do know that the early model intake ports were larger than the later T/GT 500's. Mismatched cylinders from previous owner or previous owner messing around with his dremmel tool? I am not sure exactly what you have now or whether is it a big problem or not. Here is hoping someone can add some information that may help you. Good luck

CaptCatFish · Posted: Sun Jul 18, 2010 12:36 am Post subject:

Yep I've got pictures but am having difficulty reducing them to the right size and height for the attachment requirements. I'll keep trying.........

Jim

CaptCatFish · Posted: Sun Jul 18, 2010 4:08 am Post subject:

After "googling" different port configurations, it does in fact appear that my left side cylinder is probably original but the right side is from a later model T or GT500, based on the size of the bridge in the port (relative to the left side) and the longer length of the studs which hold the carb inlet boot.

So assuming the piston sizes are the same (I'll check today), any opinions about whether or not to just button it up as is and tune accordingly or should I tear it down and match the cylinders as necessary?

Thanks!

Jim

CaptCatFish · Posted: Sun Jul 18, 2010 9:31 am Post subject:

Looks like both pistons are the same size (.5 oversize) and that the engine has been rebuilt recently in its 38 year life as evidenced by the hatch marks in the cylinders and lack of carbon on top of each piston.

Since finding the next oversize piston (1.0 ??) and ring kit has proved difficult (found the pistons but the usual sources don't have the 1.0 oversize rings) my inclination is to button it up and ride since the only difference between the cylinders seems to be that bridge in the intake port on the right side.

Any opinions? Thoughts? Comments?

CaptCatFish (Jim)

dorT500 · Posted: Sun Jul 18, 2010 6:23 pm Post subject:

dorT500 · Posted: Mon Jul 19, 2010 5:10 am Post subject:

CaptCatFish · Posted: Tue Jul 20, 2010 3:41 am Post subject:

After looking at cylinders for sale on ebay, I'm convinced my right side cylinder is from a 1976 (or later) GT500. Soooooooooooo it appears I have the original 1972 T500 cylinder on the left and a 1976 or later GT500 cylinder on the right.

Since both have the same oversize piston (.5) and it appears both cylinders have recently (relative to the age of the bike) been bored and honed, I have decided to remove both barrels and pistons, wet-sand any high spots on the pistons, lightly hone the cylinders and then finally, button it up and ride it like I stole it.

More as the saga unfolds. Thank you DORT500 for helping me get the pics posted.

CaptCatFish

dorT500 · Posted: Tue Jul 20, 2010 4:44 am Post subject:

There may be one other thing to consider. Aside from the 'configuration'....are the actual ports the same size? The 1972 T500J (larger intake ports) had size 150 main jets....the later models (smaller intake ports) had 97.5 main jets.

CaptCatFish · Posted: Wed Jul 21, 2010 1:15 am Post subject:

Your point about the jetting differences is a really good one and one I had not thought about.

I'm beginning to think the best solution is to need to clean up the right side cylinder from my 1972 donor motor (which is also .5 oversize). It has the same size and configuration as the left side cylinder since it is also from a 1972 T500. I'll get it miked and measured to see if its within tolerances for honing and using as is with the .5 oversize piston (which is almost brand new) currently used in the 1976 GT cylinder. If its not within specs, looks like I'll be scrambling to find the 1.0 piston and ring kits for both cylinders, an expense I had hoped to avoid right now.

Expense aside, it seems to me that switching back to correct cylinders for this model this makes more sense in the long term than trying to tune two cylinders on the same bike with very different jetting.

More as check into it.

Thanks again DorT500.

Jim

CaptCatFish · Posted: Mon Jul 26, 2010 2:48 am Post subject:

Thank God for a donor motor! I've cleaned up the right side cylinder from my donor motor, had it checked and honed for the (relatively) new .5 oversize pistons/rings that were in the bike when I bought it.

I've had a lot of fun cleaning up the pistons with 1000 grit wet-sandpaper. Since they had a little run time on them, I wet-sanded both until any score marks or scuffs are slicker than owl do-do. Plus I radiused all the cylinder port edges and piston skirt edges with a small stone (and 1000 grit wet sandpaper) to minimize any chance of snagging a ring.

And finally I followed the original Suzuki manual suggestions for performance enhancements by scribing in the alignment of the ports and filing about 1mm from the top of the pistons so that the ports would open just a little sooner and close just a little later. Of course all area that was wet-sanded and smoothed to a bright sheen.

Can't wait to fire this up and go for a ride. I just hope the brakes are equal to the performance enhancements.............. Smile

More when it comes to life.

CaptCatFish (aka: Jim)

Russell · Posted: Mon Jul 26, 2010 3:04 am Post subject:

Sounds great. You know for it's time the T500 double leader front brake was a pretty strong performer.T500 hubs are widely sought for use on other models in classic racing categories.

CaptCatFish · Posted: Thu Jul 29, 2010 11:49 pm Post subject:

Others had mentioned that the front double link brakes on the T500 were almost as good as disc brakes provided I took the time to set them up right.

At the moment they work really well so I'll do my best to keep them working that way. I'd really not like to graft on the front end of a GT500 or some other with disc brakes because it would change the entire appearance of the bike.

CaptCatFish

Russell · Posted: Fri Jul 30, 2010 12:26 am Post subject:

I'm not sure about a comparison with disks but I do know that they seemed to be considerably superior to other front drum brakes available at the time and for classic racing the only drum even better is the first of the GT550/750 drums with double sided twin leading shoe brake. The initial sliding caliper disk set-up that followed these may have had a touch more power in dry conditions but lost braking power badly when wet. The drum brake does not have that problem.A well set up T350 or T500 drum brake could 'chirp' the front wheel in dry conditions. Why would you need more braking power than that? The reality is that the drum when well set-up had as much power as the ribbed tyre and modest front fork of the time could cope with.

CaptCatFish · Posted: Sun Aug 29, 2010 4:45 am Post subject:

Well I finally got the thing back together with matching cylinders, new gaskets, intake boots, air filter, new rear brakes, new points and condensers, new fork seals and boots, new outer crank seals, etc., etc., and had it running yesterday. What a hoot! That thing is fast and makes a howling sound like an escapee from Hades. No wonder the Suzuki Titan 500 was "King of the Hill" for a few years until the Kawasaki triples came into play.

I'm now checking the ignition system for proper charging rates. My (new) battery is showing 12.3 volts with the key off, drops to 11.4 volts with the key on, then goes back up to 12.3-12.5 volts while the engine is running at 3K rpms and up.

Does this charging rate sound sufficient to keep the ignition system happy or should it be more (for some reason I thought it should show around 13-14 volts while running)? I don't know how to determine whether the alternator or rectifier needs additional attention (if this rate is not sufficient).

Thanks to anyone with knowledge or experience about this.

Jim (aka - CaptCatFish)