Vintage Dirt Bike Q & A

NEW MEMBER. Was browsing different forums and found this one to be most helpful, with a wealth of information. I hope someone can help me with my problem.
I recently aquired a 1975 Mr 175 elsinore from a freind that moved here, (Western North Carolina) from Texas. The bike had been stored in a shed about 13 years when he gave it to me. Motor would not fire, checked and cleaned points replaced a badly worn woodruff key. Got motor started but was running rich.Disassembled carb,cleaned, reassembled. Run decent from 1/2 to full throttle ,but will not idle. Removed the breather tube between carb and filter box. started , and carb is blowing fuel out the rear and saturating the frame. Was getting some fuel through the overflow. Adjusted float to 20 mm , got better mid to top end speed without cutting out but still getting alot of fuel out the rear of carb at low rpm's and still wont idle.I turned fuel supply of to run out fuel in carb bowl, as it starts to run out of fuel it will idle up on its on and has better throttle response before it runs out . Thought jetting might be different from Texas to here am not sure and dont know if it would make that much difference, Never messed with jetting much. Any help would be appreciated Thanks, David.

David,

Here's a pretty good thread to check out, and there are others as well:

viewtopic.php?f=21&t=2683&view=next

My initial MR175 experience was almost identical to yours, except I didn't know how many years mine spent in a shed.

My original carb needle & needle jet were toast (corroded/pitted) and just pouring fuel into the motor below 1/2 throttle. Long story short, I replaced them both (Honda P/N 16012-373-004) with NOS units from eBay, and the bike ran great.

You can replace the carb with a new one or a better-condition used one off eBay, or you can re-jet yours now with available parts and live with some excessive richness until you find a needle/jet set (the 16012-358-034 set is a bit leaner but will also work, I found two of these for sale now). Let me know which path you'd prefer to take (replace, rebuild, etc.).

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

Ray
Thanks for the reply. I dont want to replace, if I dont have to, I just like to make old things work ,if you know what I mean. It may come to replacing , because I would like the bike to be right. I would like to replace pilot jet ,needle and needle jet ,all were tarnished pretty bad, although I did not see any pitting . If I can get these parts, even if it takes a while that is fine, I'm learning that these things dont just happen over night with this bike. I have only had the bike about a month and it's been a joy to work on. I will use the part # you gave me (Honda P/N 16012-373-004) and start searching. If you could give me any more leads that would be great.I would be interested in the jet set also 16012-358-034.
Thanks alot
David

David,

OK, that's the same approach I took as well. I don't know how much better a new carb might have been, but the original one is working very well for me now, so I guess it doesn't matter.

CMNSL in Holland is actually having a 'sale' on the 16012-358-034 needle/jet sets; 18 euros plus shipping (about $23). If the part were still available as OEM, it would cost about $32. Here's the link:

http://www.cmsnl.com/products/needle-se ... 012358024/

I couldn't find anyone currently selling the 16012-373-004 set.

Jets 'r Us has the jets; I'd suggest getting a #115 and #118 main, and a #48 and #50 pilot. I usually buy the 'genuine Keihin' jets, but I've used both types they sell with good results. Right now I'm running the 115/48 setup, and that's what I'd suggest you use too.

Main: http://www.jetsrus.com/a_jets_by_carbur ... 25-xxx.htm

Pilot: http://www.jetsrus.com/a_jets_by_carbur ... 29-xxx.htm

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

Ray
I want to say,THANKS again. You are a mountain of info. Parts are ordered. Will keep you posted on the bikes progress.
David

Ray
Got the parts for the carb, Finally got time to put it back together, and it runs great. Thanks again for all your help. David

David,

Glad to hear you got the bike working well, and you're welcome! If any other issues crop up, just give a shout.

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