Suzuki DT150 Super Six carburetor help

[skhagler]

Gents,

New member to the forum. I have a Suzuki DT150 Super Six that I purchased about a month ago, serial number 15001-601593. Everything I've found (Boats.net, Brownspoint.net, etc.) shows this to be a 1986 year motor. However, while rebuilding the carburetors, they don't appear to be the original one for the motor. The top and middle carbs both have 87D30 stamped on their housing and 55 stamped on the butterflies; main jet size was 132.5 and pilot jet size was 85. The bottom carb has 88D02 stamped on the housing and 60 stamped on the butterflies; main jet size was 132.5 and pilot jet size was 90. It is easy to see visually that the bottom carb inlet and butterflies are larger than the top and middle carbs. I assume the stamping on the butterflies (55 and 60) is the size in mm, correct me if I'm wrong (plan on measuring tomorrow with the Veneer).

It looks like the bottom carb is for a 1986 DT200 from what I could research, but with smaller main jets installed. What I can't find however, and am hoping someone can chime in, is what model the top and middle carbs are. No parts manual I looked at on Brownspoint or Boats.net showed a carb with this part number. Any input would be greatly appreciated.

Also, I assume I will have to change up carbs so that they all match; I wouldn't think they could be synchronized with one having a larger inlet and butterflies. But, doesn't hurt to ask; if I use the two different size carbs, but swap out the main and pilot jets so that the jets are all the same between the three carbs, will the engine run ok or would the one with the larger butterflies run leaner or would there be enough of a power imbalance to cause issues? Again, any input would be greatly appreciated.

[Solarman]

On some of the older model DT motors, carbs and jets were not all identical between top, middle, and bottom carbs. This was that way from factory, to balance vacuum and pressures between cylinders when running. This also, does not mean your carbs should be different. It is possible someone may have replaced one for some reason (possibly from a scrap yard?). As many parts are not available now?

If the parts listing shows different jets for the carbs, you should correct that. But the factory would not have used 6 different size jets. Generally it would only be 2 jets different, and it would usually be in the middle, or bottom carb.

Also, if you click on the name/part # of the carb, it will list all of the years, and model motors that part was used on.

Often there is a different part# on one or more parts like carbs, if there are different attachments that need to be installed on that carb (throttle valve sensor, for example).

Usually any differences between certain parts, like carbs, would have a reference reason, in the specific Suzuki service manual for that motor.

One thing all the Suzuki motor carbs have in common, is that all the manuals only list one "idle air-mixture" setting for each model, no matter how many carbs. This means all "idle air-mixture" screws are set identically, per the manual, between all carbs, usually one for each cylinder.
But you have 3 dual carbs, on your motor, but still each cylinder has its own carb, and mixture screw.

When cleaning Suzuki carbs, it is very important to blow each pas-sage (fuel or air), every little hole, clear with compressed air, to make sure the air-fuel ratio is exactly like it was at the factory.

Hope this has helped you in some way.

Good luck, post back when able to let us know.

[skhagler]

Thanks for the reply and info Solarman. I agree that minor changes to carbs was most likely made from the factory for balancing, but the larger inlet and butterflies I have on the bottom doesn't seem to fit and I suspect what you posted; that some time in the past, the bottom carb was replaced by person X.

I measured the butterflies and the top and middle carbs both measure ~1.413" while the butterflies on the bottom carb measures ~1.569". This does not add up to 55mm or 60mm, so my assumption that the stamping on the butterflies correlates to mm size is wrong. What it does add up to is as follows:
1.413" ~ 36mm
1.569" ~ 40mm

Mikuni carb part numbers uses the first digit as the throttle inlet size. Per Suzuki manual, the following carbs were used:
BW40-32, used on all DT200
BW40-28, used on all DT175 and 1986 DT150/DT150SS
BW36-24, used on all DT150/DT150SS after 1986

So, what I have is the proper carbs on the top and middle, and either a DT175 or DT200 carb with different jet sizes on the bottom. I would think that the larger inlet and butterfly size on the bottom carb would cause the bottom two cylinders to have more power/higher combustion pressure than the others and would not allow balancing of the engine.

Even worst is the bottom carb with the smaller main jet which surely was causing a lean condition. Based on the jet sizes I found in the carbs, they do not appear to be set up for a 1986 motor either; 1986 parts manual does not even list a 132.5 main jet size or a 85 pilot jet size. 1987 manual does and says the 132.5 main jet is for both the DT150 and DT150 Super Six, the 85 pilot jet is for a DT175, and the 90 pilot jet is for a DT200. Thank goodness the pistons aren't fried.

To correct, I found a set of DT200 carbs I will be installing. Since the Super Six already uses all 8 reeds, this will essentially give me a DT200. Thanks again for the info and hope the information here helps others along the way.

[Kitchen940]

skhagler,

I have an 87 DT 175 that I just tore down to rebuild but come to find out a piece of my crankcase has blown apart so it is scrap. I found a 94 super 6 dt 150 powerhead that I want to drop on if it will work. Do you or anyone know the differences from the 150 to 175 to 200? A lot of the stuff on browns point looks similar. I'm sure it will bolt on I am just trying to figure out if wiring is the same and if I just threw my 175 carbs on if it would essentially make the 150 a 175 again. I know from 175 to a 200 I was pretty sure it was just the difference in carbs. Thanks


-Dan

[Solarman]

From 87 to 94 a number of changes were made in those motors. It would surprise me if they are the same bolt pattern? The only way to know for sure is to click on each item's part number and see what motors those parts were used on. It should give you a list of motors, different models, and horse power.

Good luck.

[Kitchen940]

Just an update, purchased a 94 dt150 powerhead with dual plugs on each cyl off e bay. I think this is a super 6 model? I don’t know the s/n and the seller didn’t keep track when he took it apart so really not 100% on the year. It is gray though not white. Everything bolted up and I through my dt 175 carbs on it and she fired right up. All electrical plugged in as well. I did notice that this motor does not have the fine idle adjustment knob and oil reset button like my 175 has but that looks like the only difference. We will see how she runs soon when I get it to the lake! Actually was a very easy swap too.

[Dbranas]

Hello all and thanks for keeping this site up. Got this engine DT200 and it used to start right up and all of the sudden now does not start, it tries to but for 1 or 2 seconds, the carbs are full of fuel, the spark plugs brand new, however, the sparks are on the orange side, I ordered a manual and it is on its way but I was wondering if there is any quick test that I could try in the mean time...is the spark color supposed to be orange or blueish?..I have even tried new fuel on a separate tank and same results...cranks but does not start...any help? Thanks.