Lyster Suzuki T500 build

[smokin_blue]

Hello all, I thought I would start to log a build of my new project. I will warn you all up front of two things. First this build will probably take a while. My builds are what I do for mental therapy but it is always prioritized behind working full time and trying to chase down my two teenage kids. Second this project will probably tick off the purists but I don't have the budget or the interest to build a pure 1970 bike.

So the goal of this project is to build a one off custom using a Colin Lyster frame and a T500 engine. The vision right now is to build a 1970 road race bike for street use using a mix of 1970's parts and more modern parts. This project will be in two phases. The first is to do a very rough build just enough to get through the titling process. Once I have it titled I will then build it the way I really want it.

The back story of this project has two angles. First I was getting towards the end of building Cafe a la Carte and I was designing and machining a brake/fork brace set up for a '73 Triumph a buddy of mine on the east coast was building. I had agreed in trade for the work he was going to give me a Colin Lyster frame. Second, once I got the frame I had to figure out what engine to put in it. I had been missing having a two stroke since I had sold Smokin Blue about 10 years before. So the more I thought about it the frame needed a T500. I had been resisting filling my need for a two stroke with a 40+ year old bike but since it was big brother to Smokin Blue it just seemed right.

So a little history about the frame. Colin Lyster was a Rhodesian racer who over the years lived in many countries. At the time I believe he was living in England. He was both a racer and a bit of an innovator. He both designed his own frames as well as developed his own disk brake systems. He ran triple disks long before anyone else did. I read somewhere that he sold his brake designs to Lockhart before he was all done. Colin built his own frames as well as designed and built some for other race efforts. He raced with a CB450 and ran heads of his own design.

He sold frames into the US through IMI (International Motorcycles Incorporated) of Lancaster, Pennsylvania. In one article he was listed as being their Head of Engineering. The frames in the US were mainly sold to racers and were of one of two designs. One was designed for a Honda CB450 and the other was for a Triumph 650. Later they sold a hardtail chopper frame designed for the CB450 which I found as a wild shift from his racing focus. The frames were made of chrome molly and all bronze welded. They were built by Grand Prix Metalcraft who supported the Formula 1 racing effort in England.

I found a T500 that looked pretty good from 50 feet. I was told it was a 1973 but once I went to see it I found out it was a 1972 with bent forks and a mismatch of parts. Ultimately there were some good points like it had brand new stock size pistons and rings and brand new OEM cables. It was the start of a restoration project that the owner lost interest in. Overall it was in ok shape after having driven 400 miles I decided to buy it.

The frame I have was designed to run a Honda CB450. It was very rough in that it had 40 years of surface rust from being stored in a shed on the east coast.

Here is the frame as I received it.




Here is the bike loaded up and ready to drive home.

[smokin_blue]

Here is a picture after the frame was sand blasted.



Here it is from the front



Here you can see the bronze welding.





Here is the frame with the engine sitting in it.



The pitting of the frame was fairly heavy but also was overall very even. I thought about doing a bunch of filler work and painting the frame but I just didn't want to do that. My original plan was to clear coat it so the bronze welding would show. My painter advised against automotive clear coat so I went to my powder coater. He advised not going with clear because he really felt the pits could start to bloom rust in a few years. I just couldn't bring myself to painting it as is and was torn on how to go forward.

This build was going to be unique so it is going to go forward with all it's character flaws. So then after much debating with an old friend I decided that we should go with nickel plating.

Here is the frame nickel plated. Character flaws and all.

[Warehouse1001]

Good choice on the plating. The pitting looks so uniform it kind of looks natural.....Part of the design. Chuck

[dgoodsy]

that does look like a good start! It is too bad that the powdercoater was hesitant to clear it, that visible bronze welding would look so cool! It really does look pretty good the way it turned out anyway though.

[smokin_blue]

I have a question that I am hoping some of the experts can help me with. This is regarding the differences in the carburetors that were used on the T500 and which version I should use. I picked up on this due to a discussion on another thread but didn't want to derail that thread.

I have two complete bikes and one spare engine. I am currently building one and saving the other as parts. They are a 1970 that appears to be pretty much entirely year correct. The second is a 1972 that has a few wrong parts on it (such as the color of the gas tank, two different cylinders -one with the intake web and one without) etc. The bike was the start of a sloppy restoration project so I don't trust how many parts are year correct. However I am building my Lyster with the 1972 engine. The bottom end is done and I am bolting down the top.

Now for carburetors, I pulled out my carburetors and I have two types it appears. I have not been able to find any of the stamped numbers that were mentioned in the other posting.

Here is what I can say:
Set 1 from the 1970 bike: These have a 44mm ID to the bellmouth and a 33mm ID to the outlet to the manifold. They are mounted on rubber flanged manifolds. They have the bowl vented to the roof of the bellmouth and run round 160 mains. They also have side pull slide caps (cable is off to the side) but they do not run the rod style idle adjuster, they are side screw idle adjusters.

Set 2 from the 1972 bike: These look and measure the same at a 44mm ID to the bellmouth and a 33mm id to the outlet to the manifold. They are mounted on rubber flanged manifolds. These however have the bowl vented to atmosphere and run round 97.5 mains. The slide caps are different in that they have center pull caps (cable is on center) and they are side screw idle adjusters.

My questions are do these sound like they are the correct carbs for the years noted? And based on the other discussion should I be going forward with the Atmosphere vented carbs rather than the HP (bellmouth vented) carbs?

Thanks!!!

[oldjapanesebikes]

I have not been able to find any of the stamped numbers that were mentioned in the other posting.

Nothing on the top bridge at all ?

[ConnerVT]

I wont profess to be an "Expert" regarding this subject, but I will pass on my thoughts, pulled together from 5 years of reading, as well as trial and (many) error dealing with my bitsa T500.

It sounds you are spot on on your assessment, that you have both an early and late model set of carbs. Along with the differences between homopressure and external venting, and the main jet size, the later carb has a different jet needle, which has a slightly richer taper. The late carbs are all P-4 needle jet, where the early ones, depending on year, sometimes were fitted with P-5 in the right side carb.

Which is better? That's a hard one to say for sure, as more trial (and even more errors) would be required. The homopressure carbs were a great idea that were troublesome in the real world. They were meant to handle changes in atmospheric pressure (sea level vs altitude), but created their own issues at certain throttle opening and RPMs. I am running them, but still haven't found a setting where I'm 100% happy across all riding possibilities. But I'm close enough.

When Suzuki made changes in 1973, they either did it to ditch the homopressure carbs, or to detune the motor to make the GT550 the more noticeably powerful motor. Only some Suzuki engineers, either dead or enjoying late retirement, know for certain. They made a number of other changes, along with the carbs, which make it difficult to directly compare the two on stock configured motorcycles:

Cylinder head: The earlier cylinder does not have a divider in the intake, vs the later model. Some here strongly feel the early cylinder generates more power, but I haven't had an opportunity to compare.

Intake manifold: The early intake manifold is significantly shorter than the late model. Shorter manifold length usually means a stronger "signal" (difference in pressure which the carb responds), so faster response to throttle changes. Early intakes are one piece, with a flange molded to the rubber boot. Late intakes have a separate flange and rubber boot.

Air box and filter: Some say the late model (with foam filter) is less restrictive. Myself, I feel that they are likely the same, and any difference is due to the filter element used on a particular bike. What condition is a NOS 45 year old paper element? Easier to ask about the 40 year old OEM filter. It is now black dust powder. So the replacement filter element may be better or worse than what the Suzuki engineers had 40 years ago. The boots between the air box and carbs are nearly identical. There are 2 different parts, as the late model boot has a little indentation, to allow clearance of the tach cable as the longer intakes moved everything else back about an inch.

So a lot to digest. Which to go with? It would be interesting to see how the late model carbs run on the early bike. I'd might try going one up on the main jets (100.0), and maybe a shim (1/2 notch) on the jet needles to start, just to make sure you are not too lean. Otherwise, the early stock homopressure carbs (as the truly stock config) is never a bad way to go.

[smokin_blue]

OJB:
I checked both sets of carbs and I have no marks at all on that bridge. The floats are brass on both sets

Conner:
So I dug in a little deeper and found the following

std set (vented to atmosphere) are running a 5FP17 needle and the slide is long at 53mm with a 2.5 cut out so these must be 1973 or newer carbs then since they have the 5FP17 and the 97.5 main would that be correct? unless they put newer needles in the older carbs. I will have to pull the needle jets and see if they are 72 spec or '73 spec jets. The engine number checked out correct for '72 at T500-50431.

homo pressure set are running 5FP8 on both left and right carbs and the slide is noticeably shorter at 41mm with a 2.5 cut out I am guessing these are correct then for 1970. The engine is a '70 at T500-24703


And if I read your past notes correctly I should run the vented set rather than the HP set. (the cylinders were ported by Eric and it will run pods and expansion chambers)

[ConnerVT]

Since your motor is going to be far from stock, I would use the later model carbs. This will remove the, for lack of a better word, vagueness of the HP carbs. Mikuni carbs are really straightforward, when you look at each of the circuits independently. High pressure on one side, lower pressure on the other, and an orifice in between. High pressure moves to low pressure, orifice meters how fast (how much over time) can pass.

With the HP carbs, the high pressure side is also tied to the low pressure side. So now you have two variables changing (both high and low pressure sides), rather than just one (low pressure). Again, it was a great idea, just a bear to make it work.

If you can make all of the bits fit together, I would suggest using the shorter,early (one piece) intakes. I don't know what you are planning for an air filter (Air box? Pods?).

Given that you are working the cylinders, and new exhaust, I'd probably start 3 (4?) sizes up on the mains from the 97.5. That would put you at 105 (107.5). I'd also recommend the shim kit from Exhaust Gas Technologies. The kit comes with shims that allow you to lift the jet needles 1/4 a notch at a time. I was surprised how much difference even 1/4 makes.

[smokin_blue]

Thanks for the details! I will be running pod filters. I will go thru the newer carbs and make sure the the previous owner didn't mix and match jets or anything. I do have the short rubber flanged intake manifolds and Eric matched the ports to them when he did the porting.

Thanks for the link on the shims. I do have a full machine shop but at that price it is hardly worth messing around making shims.

I have thought about possibly running either EGT or A/F guages. Does anyone have any high recommendations for either? I have a nice A/F setup that I used to jet my cafe build (4 stroke) but I know most broad band sensors will be quickly destroyed by the oil in the exhaust. Does anyone on this site use or run A/F sensors on 2 strokes for setting the jetting?

[Jimroid]

I know of no one using A/F gauges for tuning two strokes. Back in the day I had a gang of sled friends that tried egt gauges. Those seemed pretty worthless. A buddy uses egt on his RD dragbike with mixed results. Others results may vary.

[Zunspec4]

Hi smokin_blue,

You have ported barrels and will be using pipes. Is it worth asking the tuner what he recommends wrt to carbs. Personally I would forego the std. Suzuki carbs, they will turn out to be a limiting factor on a tuned engine. I guess it does depend on your budget but Titan Performance was trying out a set of much cheaper performance carbs than the normal after market Mikuni/Keine carbs, he might have some ideas too.

The set-up I am using is a set of 34mm VM Mikunis + 34mm inlets that bolt directly to the barrels.


I can at least get all the necessary jets/slides/needles etc off-the-shelf easily from the distributor, something probably not possible with the old carbs.

Cheers Geoff

[johnu]

I have the same setup as Geoff. Carbs $100 each off of Amazon. I also had Eric port my cylinders too so probably very similar set ups

[smokin_blue]

I have no issue spending the money for a set of basic VM carbs. I just have to figure out how to get the jetting close. What I need to decide is if I can run the A/F gauge that I have and get it jetted before I ruin the wide band sensor. Sounds like if you warm up the bike ahead of time and then pop the sensor in you can avoid a lot of the damage issues of a two stroke. I need to do some more reading on that side of things. I might be getting a hold of you sometime to discuss what jetting you ended up with.

[Zunspec4]

Hi smokin,

To get your engine set up some time on a dyno is the best way to go IMHO. The outfits I have used measure the A/F ratio as a matter of course and the A/F sensor they use seems to handle a 2-st exhaust without issue. Your problem will be to find a Dyno operator experienced with 2-st's rather than one who just expects to tweak a Power Commander via a laptop. Maybe one who does Moto-X work.

The use of an EGT or a Head Temp sensor I see as something more useful when you are riding the machine as an indication of how the engine is coping. If you see the Temp rising into your particular "no go zone" you can then back-off a tad to let the temp fall etc. There seems to be several here who could advise on carb set-up for those initial runs, basically conservative ign. advance and a rich carb setting to start. Where you go from there depends on your individual state of engine/pipe tune. When I first ran my restored T500 road bike everything was absolutely as per the Suzuki workshop manual but still needed tweaking wrt Main/Pilot jets, needle position etc.

Good luck

Geoff