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Suzuki T500 Carbs on a CB450 K0

teebo

teebo

Veteran Member
Joined
Dec 5, 2021
Total Posts
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Location
Oklahoma City
Inspired by Jays100 post about the PWK33, and my complete discouragement with getting my BB tuned using 14's, I resolved to try something different. I'd like to take credit for this idea but it's all Jays100. In fact, Jays100 is so old you can read about his post on HT 13 years ago: https://www.hondatwins.net/threads/t500-titan-carburetors.10430/

I've been chatting with Jays100 about it. "Chatting" is a stretch. I've been harassing him about it. He's a sport.

Motivators
- If I have to mess with trying to get my 14's tuned for my BB one more time I will either burn, part out, or turn it into an expensive art piece. I really can't decide which. Not good.
- I want to keep the stock air filter covers. But I don't mind the non-stock carbs.
- Jays100 was keen on the T500 carbs because they are Mikunis (basically a VM32), but with an inlet spigot size more conducive to fitting within the covers. 55mm vs the larger VM32 size.
- Lots O'Parts. With an asterisk.

Challenges:
- Fit. Jays100 solved most of the mystery. But it's handcrafted.
- Obviously, the jetting
- The T500 carbs, while Mikuni with all those parts, is slightly different.

So here we go. You all can witness my triumph or defeat. And learn. Or laugh.

Here is a pic of the carbs since I know you all like pictures:

AF67DA12-9C95-4E20-98AB-BB21DDB331CC.JPG
 
What do I have here? First is inspect and clean what I have.

My goal start jetting is:

25 pilot
120 main
P4 needle jet
6DH7 needle
2.5 slides

Surgery:
IMG_1722.jpeg

As is, the carbs have:

30 pilot
150 mains
P5 needle jet, Series 188*
5FP8 and 5FP17 jet needles*

I don’t know much about 2 stroke. But rich so far.

Ordered:
22.5, 25, and 25.5 pilot
120, 122.5 main
T500 carb kit for the non-jet parts

The carbs fit the stock boots perfectly. But I’ll need a spacer.

Missing idle screw springs.

Kit didn’t come with the top slide gasket. The ones on the carbs are beat.

Of benefit: One carb has an oil port, which I’ll repurpose as a vacuum port. Oddly, the other carb doesn’t but has the spot where it goes. Drill time. But why just one carb? Shared manifold?

IMG_1723.jpeg

Researching:

My carbs have Series 5 jet needles and Series 188 needle jet (emulsifier). I gather this is different from a VM32.

I’ll need to verify needle lengths. Jays mentioned the 6DH7 had to be shortened. Also, the P4 Series 188 isn’t available. Or doesn’t exist. So I’ll have to go with the Series 159 P4 and find the closest Series 5 needle. Or maybe the series 6 is better. Don’t know yet.
 
I've worked on Mikunis, but never branded Mikunis like came from a major bike manufacturers like the Keihins are from Hondas. It is interesting that the oil injection was only connected to one carb. I'm wondering if that is a vacuum feed to the oil injection pump to tell it when to feed each cylinder somewhere else, looks too large to be an actual oil feed.
 
Since this is a guess at this point, I think I will go ahead with the existing Series 188 P5 emulsifier, and the closest Series 5 needle to the 6DH7. The 5EJ11 has a similar first taper (until the end), richer at full throttle though. I can always lower the needle a notch? Is this the correct logic? I can always switch emulsifier and needle if need be. Nice to have that option.

1713452608906.png
1713452483553.png
1713452519023.png
 
I like your approach!
Also, no worries, I'll help as I can. That size and shape Mikuni was what I could find for things to still fit under the side cover. Oh, and the enrichener has a crossover linkage, me likey!

I just noticed your pilot jet size. Please double check, I don't think those ordered are correct for that year. My clue was the half sizes that weren't available then. The difference is the metering orifice is before or after the air-bleed holes.
The VM22/210 style is what is needed but I think you've ordered the BS 30/96 or 151.067 series.

Here's a look at what's available, confusing right?
1713543045358.png
 
Forgot this pic. What was in the carb is top. Of course, this assume what was in the carb was correct.

These are 8 hole and same dimensions as VM22.

The mains on that T500 page look like the VM11-22 page. Except the T500 page has half sizes.

The mystery. Lol

IMG_1778.jpeg
 
I can only say that the slow jets appear the same for the T500 and VM22 list. Same number of holes, same dimensions.

Not sure how much that is saying though.

I can’t even correlate the stamp of “156/02” on the carbs to anything. Just in an effort to understand which jets those use. Since I have no idea if someone just put some random jets in these.
 
Regarding the oil injection port on one side but not the other, I added a similar beaded tube to the other side carb, the boss was already cast in place so I made a symmetrical fitting. It was great for tuning, I could just plug in my vacuum gauge and tune away!

In longer term use this was somewhat problematic because the automotive vacuum caps I used to cover, would only last a year before they needed replacement. I don’t know if it was higher heat or sunlight but the covers I had weren’t reliable. When they failed, it was an open vacuum leak and power disappeared. What I ended up doing was taking high temp fuel hose and just connecting the two ports. Ugly (in my opinion anyway) but it worked.

Today, I’d probably paint the automotive vacuum caps in the assumption that sunlight, UV radiation, was the root cause failure mode. At least try it. Or, drill/tap for vacuum fittings and use a gasketed screw to seal (best solution).
 
It's interesting that automotive vacuum caps last so much longer on a car engine than they do on bikes. I would say the higher potential heat of an air cooled bike engine might be part of the cause, but the temperatures newer vehicles run at these days has to be close to an air cooled engine's temps. So it does make you wonder about UV exposure.
 
The bowl on one doesn’t have an overflow outlet. Not just missing the brass, but there isn’t a passage either.

I have a damaged 450 bowl with the same size brass. Going to drill out the passage, and press it in.

IMG_1784.jpeg
IMG_1785.jpeg
 
The bowl must be vented in some way, not sure you need to do that. I wonder if the T500 had a vent hose that went between the carbs to share one bowl vent... but it's just a guess, I have zero T500 knowledge except that they were one of the best Suzukis of the era and had badass front brakes.
 
ancientdad said:
The bowl must be vented in some way, not sure you need to do that. I wonder if the T500 had a vent hose that went between the carbs to share one bowl vent... but it's just a guess, I have zero T500 knowledge except that they were one of the best Suzukis of the era and had badass front brakes.
Click to expand...
I wondered the same thing. But don’t see how.
 
Turns out I couldn’t get the 5EJ11 needles. So going the P4 + 6DH7 route as Jays100 did.

Maybe smarter to not tread totally new ground anyway.
 
Jays100 said:
Nice work!
Click to expand...
Thanks. This was with a hole saw made for steel and drill press.

I did this hole to see if it would work. Have a 32mm bit coming.

Learned…clamp it down tighter. Go slooow. Getting impatient and pressing hard causes it to bite and lurch. More lubricant. I’ll probably take the drill press outside and use the hose to trickle water and keep it clean.

It’s no mill. But close enough I guess.

Now cutting it to shape: New for me also. Though reading online it seems straight forward. I have multiple tools. Just need a blade for metal. Think I’m going the miter saw route. Though I could use a band saw. The rest is sanding/filing/grinding the last little bit.
 
Certainly recommend layout (dykem for instance) and centerpunch all hole centers. Otherwise the coolant/water washes off all marks and lines during holesaw cuts.
 
I have a bit of a different plan for that too. It seems to me difficult with this equipment to get great precision.

My thought is drill the big hole first. Then position the manifold boot exactly over that hole and mark the bolt holes and outline.

Specifically, press the boot down, then lightly spray paint around the edges and bolt holes. That’s my outline, with a fairly precise and durable outline.

If I use miter saw, then drill the bolt holes and mount it to a piece of wood for stability. I’d rather not have that increasingly small piece go flying.

This is where a band saw might be better.

I could just take this to a machinist. Where is the darn fun in that?
 
teebo said:
I have a bit of a different plan for that too. It seems to me difficult with this equipment to get great precision.

My thought is drill the big hole first. Then position the manifold boot exactly over that hole and mark the bolt holes and outline.

Specifically, press the boot down, then lightly spray paint around the edges and bolt holes. That’s my outline, with a fairly precise and durable outline.

If I use miter saw, then drill the bolt holes and mount it to a piece of wood for stability. I’d rather not have that increasingly small piece go flying.

This is where a band saw might be better.

I could just take this to a machinist. Where is the darn fun in that?
Click to expand...
Mitre saws blades deflect a lot, plus the stroke is short so chip clearance, you'll have to stop and clear. I'd go way wide by an 1/8" and finish to size with a belt sander.
 
Jays100 said:
I like your approach!
Also, no worries, I'll help as I can. That size and shape Mikuni was what I could find for things to still fit under the side cover. Oh, and the enrichener has a crossover linkage, me likey!

I just noticed your pilot jet size. Please double check, I don't think those ordered are correct for that year. My clue was the half sizes that weren't available then. The difference is the metering orifice is before or after the air-bleed holes.
The VM22/210 style is what is needed but I think you've ordered the BS 30/96 or 151.067 series.

Here's a look at what's available, confusing right?
View attachment 31716
Click to expand...
I have a bit more info about this.

Recap:

- I ordered pilot and main from this list:


- Jays100 thought maybe they should have been from the VM22 list though.

- I had Series 188 P5 needle jets in the carbs, but ordered a Series 159 P4 because they are the correct length. The 159’s fit perfectly in the carb. They look the same. They aren’t.

And here is the clarity.

What I ordered from that link turns out to be VM22/210 for the pilots. However, the mains are N100.604’s. And… the mains fit the Series 188 perfectly. They do not fit the Series 159. Mains screw part way in and stick.

Because… Series 188 takes a smaller thread size (M5 X .7). The 159 is slightly larger. Which… the VM22’s are (M6 X .8).

I’m going into this detail for someone’s future use. Take all the jets out and see what you have. Measure them. Count holes. Jets R Us indicates the measurements of the pilot and main. But no indication on the emulsifier. Score one for Jets R Us I guess.

From Mikunioz.com:

“The Mikuni N100.604 main jet has a total length of 9mm with a 8m head diameter head and 5mm outside diameter of the thread. This jet is also identifiable against the VM11/22 by the machined groove around the 8mm diameter head. Be careful not to confuse this jet with other round head main jets.”

Solid advice.
 
Wow! Yet another PITA!
If you wish to keep the P4's, it appears then, that they take the hex jets??? Two things to look out for if so: 1. if the hex jets are used, ensure clearance in the float bowl 2. the hex jets are a flow standard, not orifice diameter
 
Jays100 said:
Wow! Yet another PITA!
If you wish to keep the P4's, it appears then, that they take the hex jets??? Two things to look out for if so: 1. if the hex jets are used, ensure clearance in the float bowl 2. the hex jets are a flow standard, not orifice diameter
Click to expand...
For now I’m going to stick with what was in the carb, with the matching 120 mains.

Except I do have the 6DH7’s coming.
 
You might want to invest in a set of these for getting the bolt holes center punched. Even though this is a standard as opposed to metric set it will still do wonders for your accuracy.
www.harborfreight.com

Transfer Punch Set, 28 Piece

Amazing deals on this 28Pc Transfer Punch Set at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com
 
Jays100 said:
Wow! Yet another PITA!
Click to expand...
Actually, this is time consuming but I’m relieved by all this. One of my concerns about the T500 route was if all the required parts were still available. I know it’s Mikuni, but it didn’t take me long to figure out it’s not straight up a particular model.

At any rate, it would seem I have multiple avenues for all this.

May have been easier with a new carb. But not as interesting.
 
12ozPBR said:
You might want to invest in a set of these for getting the bolt holes center punched. Even though this is a standard as opposed to metric set it will still do wonders for your accuracy.
www.harborfreight.com

Transfer Punch Set, 28 Piece

Amazing deals on this 28Pc Transfer Punch Set at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com
Click to expand...
What a great idea. Done. Ordered a metric set from Amazon.
 
So a small unplanned delay.

I’ve used power tools a countless number of times. Since I was a boy. No mishaps of significance. Was taught, a followed, that you don’t have to fear the tool, but you most certainly have to respect it.

I didn’t. All on me. You know the story. Saw catches material and drags hand into blade.

S’all good. No long term damage. Sliced up and pulverized my middle finger. Once the numbing shots wear off it’s probably going to smart a little.

To keep this post somewhat on track…

The metal blade I got for the miter saw works really well actually. Nice clean cuts. However, I should have followed my gut and used a bandsaw.
 
Yeah, when I/we remodeled our house, progress was measured in bandages.

Hope you’re okay. (And how many stitches did it take to stop the leak?)
 
Jays100 said:
Yeah, when I/we remodeled our house, progress was measured in bandages.

Hope you’re okay. (And how many stitches did it take to stop the leak?)
Click to expand...
10 stitches with a second set of hands tucking the mushy bits back in. Saw blades don’t leave nice clean cuts on skin it seems.

I constantly have damage on hands. I bet most of us do. Just the minor stuff though.
 
I hope the hand is mending well. I'd be interested in hearing more about how you're fashioning the spacers, i.e., the order of events and tools used.

Could one have opted to design spacers on the backside of the carbs to the airbox or does it have to be up front?

Nice work!
 
stl360+450 said:
I hope the hand is mending well. I'd be interested in hearing more about how you're fashioning the spacers, i.e., the order of events and tools used.

Could one have opted to design spacers on the backside of the carbs to the airbox or does it have to be up front?

Nice work!
Click to expand...
Finger is coming along. Oddly, it looks terrible but doesn’t hurt much. A little nerve damage might be a positive for this hobby.

I wish I could tell a good tale about the best way to do this without proper tools. Unfortunately, it’s mostly a “don’t do this” type thing. I have great respect for a proper machinist and tools. Here is why.

I ended up not using a band saw. My bandsaw isn’t the “for metal” variety. There is a difference and the metal capable ones are just large enough I didn’t want the clutter for just this project.

The miter or table saw work well enough I think, but I didn’t have a good way to secure a small piece. Hence the finger. With these and a good blade, probably would have been able to get fairly close to final lines. But MUST have a way to secure at any angle.

End technique was brute force. I used a metal blade on an oscillating saw to remove major pieces and a big bench belt sander with and aggressive grit belt. Takes some time, and multiple belts, but it’s safe. A bench grinder just clogged with aluminum glaze. Different wheel perhaps.

I think these pieces will pass close scrutiny when done. Not expert scrutiny. Good enough.
 
By the way. I think working with a high-heat plastic would likely be a lot easier. It’s pretty darn expensive though.
 
Here is the fit. This is without manifold gaskets. I’m thinking probably at least 2mm thinner for the spacer.

IMG_1823.jpegIMG_1824.jpegIMG_1825.jpeg
 
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I might take these to the machinist to plane thinner. Not sure I want to struggle with getting an even thickness. And flat.
 
Yes, the end result looks damn nice for basic garage work, good job. Hope the finger finishes healing up soon. I'd agree that the machinist should put the finishing touches on what you've done.
 
ancientdad said:
Yes, the end result looks damn nice for basic garage work, good job. Hope the finger finishes healing up soon. I'd agree that the machinist should put the finishing touches on what you've done.
Click to expand...
Took them to the machinist today. I don’t think it’s so easy to remove 3-4mm from these correctly. Not with a belt sander. That’s a lot of material.

I measure gasket thickness. I’m removing 4mm. Which will shorten all this around almost 3mm.
 
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