Vintage Dirt Bike Q & A

^^^^^ above I said "if I get that from ebay" I meant to say: if I get that crankshaft from ebay. Whoops.

-Ryan

When you get your new crank you might want to have it checked for tru as its gonna eat your new crank seals if its out of tru and then your gonna have to take it all apart again lol trust me I am on my fourth complete tear down of my mt250 engine and yes my crank was out of tru and it ate two sets of crank seals before I realized it was the crank being out of tru. I also kinda get the imppresion that any os piston is gonna be slightly heavier than the previous size as its bigger but I am probably wrong.

Ryan,

The eBay piston/ring set was a really good deal! If you want, you can take some of the money you saved and spend it on something that will be worth its weight in gold to you real soon:

http://cgi.ebay.com/ebaymotors/GENUINE- ... Literature

The MT250 manual shows 14-18 lb/ft for the large head bolts and 7-9 lb/ft for the small head nut, but the MT motor uses large through-bolts to hold down both the cylinder and head, like the MR175. The CR125 uses a similar all-stud setup to the MR250, and the CR numbers are 14-16.5 lb/ft for both head and cylinder nuts (all numbers are rounded off). I'd suggest 16-17 lb/ft (I use 17 on the MR).

The MT service addendum indicates the top ring is a Keystone (angled top surface) type, while the bottom is a flat ring - maybe it's the same with your rings. It's great to have the manual!

I second the suggestion about getting the crank done. It would be a shame not to do it and then wish you had later on.

Ray

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

I will ask my dad about the getting the crank checked -- he probably will say no lol . Hopefully it will be ok and just work.

And for the manual, Mitch said earlier that he would scan and email me one, but if he wouldn't be doing that for me , that would be a good investment.

Well I have been needing things to do on the bike since I am waiting for parts. Yesterday I cleaned the carb. And yesterday and today I dumped all the old rotten stinky gas out of the gas tank and burned it. Then I used Electolytic Rust Removal overnight to remove all of the rust inside. I have never tried this before and it worked quiet well!

I also took the air box side cover off to find all the foam that was supposed to be the air filter was made into a mouse nest right below it.... Yay. So I got the garden hose and hosed it all out, but now I need an air filter. Where can I get one of these?

Thanks!
Ryan

Okay, I asked my dad about checking the crank and he said that we can do it ourselves -- I didnt know we could lol. Hopefully I will be getting parts within the next few days.

Thanks,
Ryan

Call AMS Racing. They have filters for everything. Have you checked the float level on your carb?

_________________
osu_cowboy

It's tuesday and I forgot to bring my manual in to the office to scan it again today. I'll try to remember it tomorrow and email it to you before the week is out. For most things, other than carb and lights, you can go to the "manuals" section here and use the '74 CR owners manual. 99 percent of the stuff in there is the same as the MR shop manual. I have a xeroxed copy here at my office, but I'm afraid the degredation of the pictures from the copying will not be good enough to use once scanned. So I'll try and remember to bring it and scan it tomorrow. Sorry about the wait. For air filters, you can use a Uni 4025st or get one from honda for about $35. I have both, but prefer the Honda filter. Once you get the engine rebuilt you may face some problems with the carb. You might not. But with some of these older carbs, the jet needle and needle jets are worn out and the bike will run overly rich no matter how you jet them. I never could find replacement parts, so I bought a new 36mm Mikuni carb and jetted it. Love it.
Samv31: I don't have anything for 125s. Sorry.

Today the piston came. So my dad will probably take it and the cylinder into the bore shop tomorow.

I did clean the carb, and I think the float level is OK, I will try and run it and if it has problems I will adjust it.

Ok now the only thing I need before I can start assembly is crank seals. I can get the left one(25 x 55 x 10) from my local Honda dealer but the right one (38 x 64 x 13.5) is no longer available. I contacted babbitsonline and they dont have them in stock either. So, the 85 ATC250R has a crank seal with dimensions 38 x 58 x 11, so if I cant find anything the correct size, I could get a adapter sleeve made and use that seal.

If anyone has one laying around please let me know.

Thanks,
Ryan

Ryan,

I found this on eBay:

http://cgi.ebay.com/ebaymotors/NOS-Hond ... ccessories

This place might also have that seal:

http://www.select-nos-parts.com/Brothers.html

The Honda 91251-HA0-004 and 91251-HC5-005 seals are 38 x 64 x 12mm, and may just need a 1mm-thick 64mm O-ring as a spacer.

Normally I would never suggest that a differential seal be used as a crank seal, but in this case it will have gearbox oil lubrication and won't see mega-high rpm. If it were my bike, I would get the original seal.

Ray

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

I did find that 38 x 64 x 12 seal, but like you said, it is for a rear axle on a 3 wheeler. I also found that seal on ebay last night, but it is so expensive(more than we paid for the whole gasket set lol). I am in school right now but my dad is going to our local bearing, seals, belts, sprockets, pulleys, etc. supplier to see if he can find us a heavy duty or high rpm seal. If not, we probably are going to get the seal for the 85 ATC250R and get a adapter sleeve machined by our neighbor on his lathe. I will let you guys know.

Thanks for all the help.

Ryan

The correct size seal is still available. Keep looking. You can buy entire seal kits for these bikes on the 'bay for $24.99 almost any day. Look for 73-74 cr250m elsinore sets. They are the same seals on those bikes. Keep your head up.
I'm going to have to rescan the manual into several smaller parts next week. It just won't go through when I e-mail it.

Man you guys are great.

I took your suggestion and went on ebay and found this: http://cgi.ebay.com/ebaymotors/ws/eBayI ... &viewitem= , and I purchased a set. You saved the day again, Thanks!

And about the manual, Couldn't you just upload the whole thing to honda-elsinore.com so then everyone else could make use of it as well? Just a thought.

Thanks again,
Ryan

Ok I have a new dilema.

I need a nut for the flywheel. It is No longer available from honda and I haven't found it around town yet. I believe it is a 15 x 1.25 metric nut? Does anyone have one laying around?

Thanks,
Ryan

Yup got one right here from that crank thats garbage send me your address and I will let you know what shipping is I cant imagine its much as its just one nut.

Ok, Thanks, I will send you a pm.