I have a DT175 I’ve been restoring. Almost ready to go but having issues with the Carb so hoping for some help here. The bike would run with a squirt of fuel in the intake but won’t pull fuel from the bowl. I’ve cleaned the carb twice and could get it to run initially but any touch of the throttle and it would die.  The bike I’m sure is a 78’ although the vin sticker is faded and can’t be read so not entirely sure. The bike came with a 2N500 carb which appears to be factory for a 79’?  It measures at 28mm and has factory pilot/main but everything I’ve found and read suggests the bike should have a 24mm?.  Out of frustration with the carb I’ve bought a brand new Mikuni VM28 from Niche cycle also new #20 pilot and a160 main. Have t put it on yet as it seems I should have bought a 24? And maybe I should not have bought a generic VM carb?
The previous owner had dismantled the bike and the engine was removed to change the crank bearings and it never went back together.  I did replace the crank seals (dried out)  as I found out that is very important on a 2stroke. New head gasket, coil, plug.  I had a Chinese Amazon carb on it which quickly went in the trash… wouldn’t even fire with that piece o crap on it.

Any words of wisdom would be appreciated. 
 

 from near Salisbury, UK.

VIN should be stamped into one side of the headstock, as well as printed on the sticker.

If it's the original engine, then this will have the same number stamped on to it. If not, the carb needs to be matched with the engine, not the frame.

Once you have the numbers, you can look up what you have in the VIN tables in the Tech Library on this forum (see top toolbar).

If and when you find the correct carb, and some parts need replacing, use genuine Mikuni parts and not brassware from repair kits. 

Greetings from Tennessee  

The "24" is the venturi diameter which is generally down inside where the slide is located. On some Mikuni's the outlet is nearly the same diameter as the venturi... on others the outlet is a few mm larger than the venturi.

Thanks for responding! I checked the VIN on the headstock and found 3E0-000156 which doesnt match the vin tables. The engine matches the frame so that’s good.  I also checked the inner diameter of the slide and the inner diameter on the intake side of the carb and both are 28mm. So that gives me hope I ordered the right size carb at least. Whether it’s similar enough is another thing. Do you think going from a 24mm to a 28mm if it is wrong will cause lots of issues?

Are you in Canada? 3E0 shows as a Canadian market 1979 DT175F.

2N5 carb might be correct, but I don't have a Canadian parts list to refer to.

You're too quick to rubbish Chinese carbs I've used one on my 175 & runs perfect, also on a Honda 185. Look for the real cause of the problem!!. Correct crank seals as in good fit on the shaft & case. Piston in with Windows towards the inlet as that's something I've seen before & all the puff goes out the exhaust port as piston rises or goes down to a point. Over richen it to try, do something out of the ordinary like leave out the slide needle. If there's life with a squirt if juice then there's somebody home. It amazes me how 'ya all' rubbish Chinese carbs then bugger me it still doesn't run with a good mikuni etc. Ok rant over, let's get to the bottom of the cause. My carb I bought was meant to be a 28 but was finished undersized on the engine side like about 25. Still ran as it should. I guess the question has been asked, is it getting fuel in the bowl !trick!. Sorry if that sounds grumpy!!. Sometimes I wake up grumpy. Other times I let her sleep in.

From what I've read, some Chinese carbs work fine, others are sh*te - you pays yer money, you takes yer choice! 

Years ago I restored a Honda ATC200es. Put a Chinese carb on it and it ran like crap and the choke broke almost immediately. I rebuilt the original mikuni and it fired right up. So I’ll have to disagree with Chinese carbs being any good, glad they work for some though.
With this 175 it ran ok after I first cleaned the carb it came with. Shut it off as it was late at night and it wouldn’t start up after. Would only fire one in awhile. That’s what led me to buy a ‘mikuni’ off of Amazon. I’m positive spark and compression are good as I’ve tested both properly. I’ll give it a go to try and clean the original Mikuni again and use the new jets I’ve ordered for the brand new mikuni. I’m unsure if I can return the new carb at this point as well.

Oh well, let's look forward to better news soon. Cheers.