Vintage Dirt Bike Q & A

This is my first dirt bike; my first 2-stroke really. Only ever had 4-stroke street bikes, so I am learning. I got this thing for almost nothing; the PO just didn't want it. Carb is cleaned and I'm about to put it back on, but the airbox is missing. Is it ok to put an open clamp-on type filter on it? Jet mods may be necessary, yes? If so, are jets available for this thing?

Also, it needs tires. This will just be a trail bike, camp ground transport, not planning on jumping triples or anything. So I don't want to spend a bunch of money- what cheap tires are good?

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1974 Honda MR175, 1974 Honda MT250, 2003 Honda CRF150, 2003 Suzuki DRZ125, 2005 KTM 250 SXF

I've kept my airbox, as I encounter mud sometimes and hose my bike off after every ride. If you don't do either of these things, the clamp-on should be fine.

A 118 main and 48 pilot should work well with the stock motor and either filter setup. I get mine at jetsrus.com but there are other places too. Try doing a search here on the MR175, you'll pull up a ton of stuff if the search engine works properly.

I assume there must be ultra-cheap Chinese tires available now - maybe someone else can suggest something as far as that goes. I ran Kenda K270's for a while, they're fine for street and light trail use. Right now I've got Bridgestone M603/604's on it. A too-wide rear tire will rub the chain guard; a 100mm or 3.50 / 4.10 should work OK.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

I can only guess that the motor is stock. The PO dropped that and an old Suzi atv off at my buddy's shop cause he didn't want them. I traded him some furniture for them. Just got the Suzi running today, as I popped in there on my lunch break; it's an 83 and it sounds great. Hope the Elsie is the same. The mechanic just told me that the Elsie came in with just a pod on it but it was trashed and they pitched it, so I would hope that it's jetted already. Going up tomorrow to clean up the Suzi a bit and work on the Elsie. Gotta' put the carb on, but the mechanic said it has spark and seemed to have compression. Thank God jets are available at least; seems like nothing else is!

I tried searching for mr175- it said that was too common and gave me a bunch of parameters to try instead. Amusing. I'll try it again later.

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1974 Honda MR175, 1974 Honda MT250, 2003 Honda CRF150, 2003 Suzuki DRZ125, 2005 KTM 250 SXF

You could try searching my username 'rayivers' (I just pulled up 46 pages of stuff, most of it for the MR175), adding keywords as needed to narrow it down.

You're very fortunate to have spark. You may find the carb runs quite rich and doesn't respond well to jetting changes, which is probably a worn needle jet.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

I will try that; thanks.

Also, was the original needle jet brass? I was just looking at it actually, and it appears to be steel or something. My buddies mechanic first said I should replace it while appart but he saw it and said that one might be ok... looks newer.

Just realized that I have seen your thread on Thumper Talk too. This 2-stroke stuff is new to me...and seems very mystical and confusing.

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1974 Honda MR175, 1974 Honda MT250, 2003 Honda CRF150, 2003 Suzuki DRZ125, 2005 KTM 250 SXF

I've seen maybe 10 or so MR175 needle jets, all were brass and apparently identical. If your carb is stock, it should be a 28mm Keihin with 060A stamped on the body behind the choke lever.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

The carb is at my buddy's shop, along with the rest of the parts that roughly resemble what can be called a dirt bike. I will look to see if it is stock, but based on what you said that needle jet is not oem. It's clearly not brass.

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1974 Honda MR175, 1974 Honda MT250, 2003 Honda CRF150, 2003 Suzuki DRZ125, 2005 KTM 250 SXF