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hello again, and I got an mr175 for Christmas
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Author:  Mr.E [ Mon Jan 05, 2015 6:11 am ]
Post subject:  hello again, and I got an mr175 for Christmas
I've been lurking here for a long time, even registered back when I got a little '80 Cr80. But circumstances happened and it left, tho I've still been busy building bikes (classic 4 strokes). My wife found a '76 Mr175 on a yard sale site just before Christmas, and long story short, I got a $75 dollar present that I've wanted since I was a kid. And no, I didn't miss a decimal place on that price :-)

Image

Couple tiny dings in the tank, inside looks brand new too. Busted clutch cable, missing lights, and you can see the pipe - part of it, and some kind of fat expansion pipe modified to fit it.

Otherwise, it fired on the first kick with fresh fuel and clean points!

So, I'll be looking for the right head and tail lights soon, and stock exhaust too. I do see those parts on eBay, except the headlight is out of sight expensive. And in case anyone doesn't know, a '75 xl250 clutch cable is an exact match to the original :-)
Author:  rayivers [ Mon Jan 05, 2015 10:02 am ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Cool! That's an excellent price, especially for a running bike.

If you're willing to wait, I've gotten complete headlights on eBay for less than $30 shipped. I'd try to get the correct '76-'77 MR175 / MR250 all-metal unit. it's a lot more durable than the plastic-shell '75 MR / TL light with the screw tab at the bottom, and looks a bit better to me.

If the expansion chamber is an upswept type you may want to consider using it, if it's in decent shape and doesn't burn your leg. It will almost certainly make the bike run better than an unmodified stock pipe. The OEM pipe makes decent power with the internal baffles removed, though.

Ray
Author:  Mr.E [ Mon Jan 05, 2015 10:44 am ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Thanks Ray, that's good to know about the headlights. I have seen the correct tail light on eBay in nos for $68. I figured I'd grab one when I get the money saved up. As for the complete pipe, here's what it is.
Image

Previous owner ground a little off the head fins to make it fit. And its unnecessarily loud. I did consider cutting and rewelding so it exits on the side in stead of straight down too, but I really don't know anything about two strokes and how exhaust affects them.
Author:  rayivers [ Mon Jan 05, 2015 12:41 pm ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
A 'snail' pipe! I haven't seen an MR pipe like this before - it's probably a modified CR125M pipe, or something someone made up from scratch. Yeah, loud sucks. :) It looks like maybe there's some leakage here and there?

Mine's sort of similar (I'm using a different head now):

Image

2-stroke pipes are a story in themselves, but the idea is pretty simple; they pull burned exhaust out of the cylinder along with some clean fuel/air mixture, then (ideally) pop just the fuel/air back in at the right time. Megaphone-looking sections extract, reverse megaphones push back, and straight sections delay. With that in mind, your pipe appears to be tuned for a strong low-mid power hit, mine more for wideband power with added top-end (the MR175 motor's weak point).

Cutting and welding pipes obviously can be done, but if you want it to tuck in well it can be a lot of work (mine had 5 separate welding sessions). Rust can also be a problem, especially if the metal's thin.

Ray
Author:  Mr.E [ Mon Jan 05, 2015 2:36 pm ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Thanks for the info there. I think you nailed it with the Cr125 pipe. Looking at pics of them it does look like mine is made from that. It also looks like your connects to a flexible section to go back farther? To a muffler? I'd love to see any more pics of that setup. Welding up a new pipe doesn't exactly scare me, I am a toolmaker by trade, but have just never dabbled in exhaust parts or keep any of the pipe on hand.

And yeah, it's got more low end than I know what to do with. I really just want to use it as a good trail bike. *maybe* some non serious competition in my region one day, or just cutting up at the next barber vintage fest.
Author:  rayivers [ Mon Jan 05, 2015 6:05 pm ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
I poked around the Web a bit, and it's possible your pipe may have been made by Proto Pipes. Here's the type I was most familiar with:

Image

The silencer of this pipe points to the vicinity of the front sprocket; some people referred to them as 'chain oilers'. You could probably convert your pipe to this design by making a horizontal cut in the LH vertical section near the head, then rotating the cut-off section about 90° and rewelding. If you want to trade some low end for more upper midrange and top end while the pipe's apart, you can cut out that dark stained section of your pipe header near the motor mounts - this may also put the rear 'fat' part of the pipe at a better height. If you don't want to lose the low end, extend the center (largest-diameter) section the same amount as the stained section you cut out, which may be a PITA to tuck in.

You could also modify the pipe end to use a conventional silencer. Here's the left side of my bike - the silencer is an FMF Turbine Core II with stub end and mounting bracket added, and the connecting tailpipe is braided stainless with Teflon liner:

Image

Ray
Author:  Mr.E [ Mon Jan 05, 2015 7:18 pm ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Thanks aging. You've given me some good points to look into on that, and I'll see what I can do this weekend when I get my next chance to play. It does have some leakage the way it is. Although it's kinda funny to leave a trail of blue smoke everywhere I go with the exhaust pointed down. I'd like to get the pipe off the head and get a fresh head if possible - without the ground down fins at least.
Author:  rayivers [ Mon Jan 05, 2015 8:26 pm ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Well, you could always get a stock pipe for now - it would surely be a good thing to have if you ever sell the bike:
http://www.ebay.com/itm/HONDA-MR175-ELS ... 21&vxp=mtr

Unless a bunch of fins are completely removed, I wouldn't worry too much about your head, especially with a stock pipe - any reduction in cooling would be more than offset by getting that snail pipe out of the air flow.

Check this head out, it will probably make you feel much better :):
http://www.ebay.com/itm/76-honda-cr250m ... 5f&vxp=mtr

Except for the paint overspray, this head is completely original and unmodified. I would never do this to any air-cooled head, but Honda did.

Ray
Author:  Mr.E [ Tue Jan 06, 2015 8:20 am ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Ha, wow that's an interesting way to keep even cooling :shock:

I'll admit my reason for wanting to get a new head are mostly cosmetic. I do want to put this bike back as nice as I can, not totally stock, but keep it pretty clean. The stock headlight and tail light are probably the important bits to me on that. Otherwise I'm likely going to give it a fresh paint job from top to bottom sometime after spring. I was curious what other parts I may be able to use on the motor at some point. I've read some of the old articles that mention using Cr125 gears, but anything I could do with the jug/head? To the point of eventually getting a spare motor to swap in fresh. The previous owner did say it needs a bore, and the current jug only has one more bore left in it. I haven't opened it up to see for myself yet. Seems to sound good tho.
Author:  rayivers [ Tue Jan 06, 2015 2:26 pm ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Hey, my '75 main rider looked a lot worse than yours when I got it, but it's not too bad now:

Image

The first thing I did was spray my frame, motor, and wheels with Gunk Engine Brite, then hose it off - it didn't look great, but it was oil- and dirt-free. If you repainted your frame and motor and buffed out the fenders and tank, I think your bike would look real nice. Even your wheels look good; all my spokes were rusty crap and were replaced, not much could be done about the rims though.

Yes, there's all sorts of CR125M and MT125 parts that can be used on the MR175. I may build one final motor for the CR-framed bike (with the custom pipe) with a CR six-speed tranny, but that's really a track-racing gearset that's unsuitable for much else. The '77 MR175 has a fairly decent gear spread (closer-ratio than the '75-'76), but the one I like best is the MT125 box. My black bike has a '77 gearbox, the other one has MT gears 1 thru 4 and an MR 5th for a little more top speed on the road.

I've never seen an MR cylinder bored over .5mm (2nd) oversize, but the Honda OS pistons/rings go up to 1mm OS (these used to be really hard to find, seems like there's more of them nowadays). Usually the OEM ignitions don't last long enough to wear out the cylinder. Don't take a chance with the rings, they'll snap like twigs if they're old and the bore's sloppy (I almost took out my exhaust port).

Ray
Author:  Mr.E [ Sun Jan 11, 2015 12:08 pm ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Wow, that is a nice bike. What did you do to the exhaust end? I also see it's tagged. Can't do that here in NC, are there other states that allow it? My state allows tagged bikes in but won't tag an non titled anything. I've got the same tail light on my cb750 too.

Guess I'll tear the top end off next weekend and see what's going on in there. I took it out on the mountain yesterday for a couple hours, great fun. I did spray it down in purple power and engine gunk when I got it, but it's gonna need another bath now :-) the stock air filter is a mess now too. Any suggestions for what to replareplace with? I wouldn't mind dumping the air box, but don't want to hurt the motor if there's a possibility there.
Author:  rayivers [ Sun Jan 11, 2015 4:40 pm ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Thanks! CT will register nearly anything pre-81 (before 17-digit VIN numbers) with just a bill of sale. Does NC have any kind of antique/historic registration process? Sometimes that can be a back door in, if the bike/car/etc. is old enough.

I'd keep your airbox if it's complete and in decent shape (remove the top lid and snorkel though, unless you're planning on deep water crossings). You may be able to get the filter from this place:

http://www.uniflow.com.au/contents/en-us/d40.html#p502

It's about 3/4 down the page, for 'MR, SL 175' (Uni P/N NU-4026). This filter seals OK even if the foam airbox filter gasket is missing, which can be a big plus.

My pipe is a gutted MT125 unit with the heat guard & mounts removed, and the silencer is a weld-on 2t SuperTrapp converted to clamp-on. This setup makes good power and is quiet.

Ray
Author:  Mr.E [ Mon Jan 12, 2015 11:22 am ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Ha, so overnight I managed to buy the two parts for that exhaust setup too. It's gonna be nice to have no leaks. Did you have to change any jets for that?

NC doesn't like to title anything that was never intended to be titled. Antique things can get titled, but only if they previously had a title, and it's a pain to get a new one. South Carolina has recently made it easier to title barn finds, but I'm not sure that applies to non road specific bikes.

I'll probably get the stock tail light, or even a mini Lucas with tag bracket, and I've pulled a headlight off a 72 kawi g5 for now as well. I'm not above swapping tags from one of my others once in a while, but if I can keep pursuing a legal one.
Author:  rayivers [ Mon Jan 12, 2015 12:26 pm ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
You found an MT125 pipe and SuperTrapp? Or something else?

With a stock motor and carb you should be good to go with 118 main and 48 pilot jets, regardless of exhaust. You might also be interested in this slide, which is one size leaner than stock and improves 1/4 - 1/2 throttle response quite a bit; this one's a bit chewed at the top but should work fine, and is cheap:

http://www.ebay.com/itm/Misc-1612-Honda ... 5e&vxp=mtr

My friend registered his untitled MR175 in Iowa - he used an MT125 frame and went through the whole title bond / inspection / new title process. It was a pain, but the bike is now worth significantly more for the right buyer, and should sell quicker too.

The MR tail lights show up on ebay now and then. I like my Acerbis light; it took some time to install but has that really 'street legal' look I wanted.

Ray
Author:  Mr.E [ Wed Jan 14, 2015 8:11 am ]
Post subject:  Re: hello again, and I got an mr175 for Christmas
Yep, an MT 125 pipe and a small supertrapp. I used ebay and my network of friends with sheds full of spare parts. I might bite on the slide you listed tho, that sounds like a good mod. I've also found a head and jug that is still on the original bore. Just got to pace my wallet on these things. Having a family and garage full of projects makes it kinda hard sometimes. I do see MT125's once in a while here, that may be the best route for me. South Carolina is good about titling old previously titled things, and I've got friends in SC. I'll post up pics of the exhaust parts when I get them in.
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