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Author Topic: Lower frame rail repair  (Read 230 times)

Offline Hawaiiysr

Lower frame rail repair
« on: February 26, 2020, 03:06:27 AM »
This particular area of the frame sure takes a beating. It is the lowest part of the frame so it takes licks from whatever we plow over. Also being that it is the lowest moisture settles here and slowly rots the metal from the inside out. The lower motor mounts are also welded to these rails so any vibration your motor has gets transferred here. Lastly the OEM metal is thin! Check the pics


Cut out what needed to go. The stock frame rails are metric and actually rectangular not square. I don't recall the exact size off the top of my head. The closest i can get to the OEM size is 3/4" square. It is close enough that i would confidently say most people would never know a repair was made. I chose to use 1/8" wall. I didn't clean off the burrs in these pictures but you can clearly see the wall thickness difference.


New metal. Checking for fit.


My tables are not exactly flat so I put scrap down and clamp everything to the frame to keep it square. Something i found interesting was that the two lower frame rails are not symmetrical! I found this out by comparing the lengths I cut out. They were not the same length. Looking at the frame i also noticed the old welding marks differ from left to right. I made my new frame rails symmetrical. The motor does not sit dead center in the frame. It is actually offset. I never really gave it much thought before. Front motor mounts have bends in the something like this //. It all makes sense if you look closely. Motor is off set so everything else follows suit.


I use a set of dummy cases as a jig so everything lines up correctly. Head mount, swing arm, 86 rear mount since this is a 86 frame, new lower motor mounts, front motor mounts, i even use a head gasket and head torqued down. While all of this is installed I, tack everything in place and check fit once again.

All tacked up.


And that's a wrap folks.






« Last Edit: February 26, 2020, 03:44:27 AM by Hawaiiysr »

Online The norm

Re: Lower frame rail repair
« Reply #1 on: February 26, 2020, 08:20:03 AM »
Excellent write up Josh! Thanks for the contribution.
Hopefully you don't mind if I add a little something to it for guys to think about. The Honda oem frame tube is pretty much 22mm square. 3/4" is as close to 19mm as you can get and really is as you stated, so close nobody will notice the difference. I was able to source so 7/8 square tube from a local fab shop. 7/8 is damn near 22mm. 7/8" is 0.875" and 22mm is 0.866 so basically 0.009" difference. In reality it doesn't matter between 3/4" and 7/8". Anyway sorry for stepping on your write up my friend.
Loren
1986 Trx250r-- Hybrid Engineering 391(Good bye super 310)
1986 Trx250r-- Hybrid Engineering  ported stock 86 cylinder
1986 Trx250r-- craigslist engine with unknown ported 89 cylinder.
1985 Atc250r-- Needs a lot of work (Super 310's new home)

Offline Hawaiiysr

Re: Lower frame rail repair
« Reply #2 on: February 26, 2020, 12:21:50 PM »
No worries Loren. This is why we are here. Thank you for the input. I'm a bit limited on materials due to my location and green fabrication skills. Pretty sure I can order 7/8 from somewhere now days. Thank you for the measurements. If and when I need to do this repair again it will be even better with the knowledge shared. 

Online The norm

Re: Lower frame rail repair
« Reply #3 on: February 26, 2020, 12:27:14 PM »
I used 3/4 the first time I did a frame repair and then I stumbled upon 7/8" tube for my second frame. I wonder if onlinemetals would have it?
1986 Trx250r-- Hybrid Engineering 391(Good bye super 310)
1986 Trx250r-- Hybrid Engineering  ported stock 86 cylinder
1986 Trx250r-- craigslist engine with unknown ported 89 cylinder.
1985 Atc250r-- Needs a lot of work (Super 310's new home)

Offline Hawaiiysr

Re: Lower frame rail repair
« Reply #4 on: February 27, 2020, 12:18:02 PM »

quick search i found this. 2' section is $7.38. I would like a little thicker wall but this would work.

Offline havinnoj

Re: Lower frame rail repair
« Reply #5 on: February 27, 2020, 01:43:03 PM »
Nice josh!  And good work hosting on imagebam.. I like their style of ads lol.

Online The norm

Re: Lower frame rail repair
« Reply #6 on: February 27, 2020, 03:14:39 PM »
I believe the tube I got from a local fab shop was .120 wall
1986 Trx250r-- Hybrid Engineering 391(Good bye super 310)
1986 Trx250r-- Hybrid Engineering  ported stock 86 cylinder
1986 Trx250r-- craigslist engine with unknown ported 89 cylinder.
1985 Atc250r-- Needs a lot of work (Super 310's new home)

Offline broken1

Re: Lower frame rail repair
« Reply #7 on: February 27, 2020, 03:37:49 PM »
.080" wall would be perfect.
overkill is an often underrated achievement

Offline Langbolt

Re: Lower frame rail repair
« Reply #8 on: February 28, 2020, 10:26:24 AM »
Just curious.....what is the OEM Honda wall thickness for the frame tubes ???

Thanks

;)

Offline Hawaiiysr

Re: Lower frame rail repair
« Reply #9 on: February 28, 2020, 02:42:05 PM »

 

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