Turning a 1979 CR250 "barn find" into a 1978 RC250 replica

Tokyo_Tiddler 11/23/2018 1:37pm
11/23/2018 1:37pm
swatdoc wrote:
[img]https://p.vitalmx.com/photos/forums/2018/11/23/304629/s1200_7E6DBAA0_256B_41AA_B768_8284BE301671.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2018/11/23/304630/s1200_CC455ECD_977A_47DB_8F51_EABFB890AF53.jpg[/img]


A Hell Cat.. very nice John.. 707hp! Smile and under rated numbers at that. I tell every one that I have a Peter Pan complex.. I still do all the things I did when I was 18 years old. Always makes me smile when I see I am not the only one Wink
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swatdoc 11/23/2018 1:49pm
11/23/2018 1:49pm
Only difference between men and boys is the price of their toys
?
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Tokyo_Tiddler 11/23/2018 3:36pm
11/23/2018 3:36pm
Tokyo_Tiddler wrote:
Thanks Stevie, I am really grateful in your help making the VMX arm fit nicely. I wish I had just bought your arm, but it was...
Thanks Stevie,

I am really grateful in your help making the VMX arm fit nicely. I wish I had just bought your arm, but it was part of a package deal with the Fox Air Shox and a few other items. One other problem I have is the M10 footpeg bolt I got from you doesn't quite fit the ID of the heim joint on the VMX arm. The bolt has a diameter of >10mm so I can only get it on 1/5th of the way. I am now thinking about turning down the diameter of the stainless bolt with sandpaper.

I was thinking the very same thing about the rear mount Stevie.. that the only way thy could have a beefier aluminum piece in there was if it were narrower at the cases. Just looking at this pic of Joe's engine, it indeed looks narrower.


You mean this little cherry red thing from 1973? This is another former project which I built from the ground up, including the 772hp engine. The only thing I didn't do was the paint. Those wheels are custom machined billet aluminum. Took 7 months, but they did a great job. Lots of billet aluminum on this build. It is a hoot to drive.



mike



StevieD113 wrote:
She's not shy at all is she!! Ooosshhh!! Re the bolt, normally the tolerances on a bolt can be pretty big but as that goes through...
She's not shy at all is she!! Ooosshhh!!

Re the bolt, normally the tolerances on a bolt can be pretty big but as that goes through a bearing it should be 9.94 to 9.98. (it can be a little smaller, but .98 is as tight as it can get) it may have a little push off in the middle at it was turned, and I probabably missed mic-ing it in the centre. A quick polish would sort in, (litterally a minute would have down to withint the correct tolerance). My apologies for letting that one get through the net! I can do you another if you wish?

Stevie
There is more to the car than you can see in the pics.. while the driveline, suspension and brakes are all aftermarket race parts, almost the entire interior and most all of the body parts are NOS GM parts.. took me years to find. Even the seat belts are NOS.. so everything looks and works as new as it was in 1973. The car was built for a fun drive so it has a 5 speed manual and a 1200hp capable dual disc clutch which would be really harsh for a drag race launch with slicks, but more fun on the streets.

On the foot peg/ front brake arm bolt.. I got it down to size by using #320 grit sand paper and holding it tightly between my fingers will turning with a wrench for 15 or so minutes. Most of the bolt spec'd out at 9.98-9.99mm. There was one spot just after the threads where it spec'd at 10.00mm (I measured 10.08mm, yesterday, for some reason) and that was the spot that I couldn't force through the heim joint. After sanding with the above procedure it now spec's at 9.98mm along the length and fits nicely. So I am good on the bolt now.

On the spacer for the front heim joint, the joint measures 13.95mm wide. I think the overall gap between the frame rail and the inner mount for the bolt is about 20.80mm, so a ~6.85 thick spacer should do it. Is that the size you run with your arm?

mike
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Tokyo_Tiddler 11/25/2018 2:32pm
11/25/2018 2:32pm Edited Date/Time 11/25/2018 2:33pm
Here are some pics of that 1 piece beefy mount you mentioned, Stevie.



The Shop

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Tokyo_Tiddler 11/25/2018 2:52pm
11/25/2018 2:52pm Edited Date/Time 11/25/2018 8:46pm
I worked on the front end this weekend, cost the triple clamps detailed and they look even better with Stevie's RC replica bolts. I decided not to paint the handlebars and just gave them a polish and wax.. I think it is cool to see the original paint. When I took off the triple clamps and swing arm, they were still packed with plenty of yellow grease from the factory!!

It takes me about 2 hours to detail each wheel. Each spoke nipple is moved back and forth a few times to make sure it is free. The bolts are replaced with NOS pieces.

For the forks, I first strip off the silver coating with WD40 and a 3M pad.. takes a while, but once off, it polishes right up in minutes. It will stay looking great for a long time as long as you don't get it wet and it polishes like new again in a few minutes. They sell a wipe on sealer to keep polished aluminum shiny, but I have never tried it. I don't mind spending literally 2 minutes to put a fresh polish on her. Aluminum is easy to keep looking like new!

All I have left to do is assemble the forks and wait for the remaining parts before I can finish her.

Tokyo_Tiddler 11/25/2018 8:44pm
11/25/2018 8:44pm Edited Date/Time 11/26/2018 1:12am
On the suspension, a few things have come back to me that I had long forgotten such as the difference between the black and the silver Fox Air Shox. The black ones didn't have a topping out mechanism so they snap back with a click. Fox introduced a topping out valve in the silver ones to eliminate that annoying click. I had the silver ones on my CR250 in 1979 and a friend had the black ones one his 1978 CR250.. once I pushed down on the current blacks ones I have.. it all came back when I heard that click.

On the forks, I bought the heavier .48kg springs from Race Tech as I no longer weigh 148lbs like I did in 1979. The OEM spring is just .23kg with no stiffer options from Honda!! The soft springs is what held me back from going faster on jump filled tracks, I recall, and the spring rate decided by Honda is silly. The spring Race Tech Recommended is more than double the rate that Honda originally spec'd!!!!!!! Now the only way to control rebound with these old forks is heavier oil and the rebound will be much faster with the >2X stiffer spring rate, so they recommended 15weight oil instead of the OEM recommended 5 weight oil.

I am hesitating doing the Al Baker mod of drilling the 1mm to 1.5mm hole 2" from the bottom of the dampening rod as I fear that may speed up rebound too much with the much heavier fork spring. Need to figure this out and will talk to Race Tech tomorrow. The fork springs they provide are smaller diameter and much shorter than the OEM spring so Race Tech provides a couple of short lengths of PVC pipe to make up the difference and establish proper preload. I was wondering if I should eliminate the super wimpy soft upper spring in the OEM fork like the factory team did and make up the difference with a longer section of PVC pipe. I have a few things to figure out.
StevieD113 11/26/2018 5:58am
11/26/2018 5:58am
Tokyo_Tiddler wrote:
Here are some pics of that 1 piece beefy mount you mentioned, Stevie. [img]https://p.vitalmx.com/photos/forums/2018/11/25/305341/s1200_tydog_mount_2.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2018/11/25/305340/s1200_Tydog_mount_3.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2018/11/25/305339/s1200_Tydogs_rear_mount.jpg[/img]
Here are some pics of that 1 piece beefy mount you mentioned, Stevie.



This is the one on Marty's 79 RC. It's a little different as it has flat sides. Leading me to the conclusion that it had narrower cases at the rear mounts.



I have one all designed. But it will require slightly longer bolts. As it's going to be little chunkier than the OEM steel one.

Stevie
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Tokyo_Tiddler 11/26/2018 6:14am
11/26/2018 6:14am
The chunkier the better for this piece. You can see how the person who did the 1 piece above solved that by recessing the spot where the swingarm dust shields touch the mount. Even the Marty Smith piece has the ears milled a bit more for the cases trying to make as strong as a mount that will fit in there.
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Tokyo_Tiddler 12/1/2018 12:38pm
12/1/2018 12:38pm
I was looking around for some fork wipers that would fit so it would look more like the factory forks Honda ran in 1978 without the fork boots. It is a cleaner look, I think. The first 2 types I bought looked like crap on there so I was going to run without them. Should have guessed there would be trouble when they advertise they fit a range of fork tub sizes. Then I ran into these made specifically for 37mm fork tubes by "Leak Proof Fork Seals". Much nicer rubber and they fit perfectly. They fit snugly around the lower tubes so I doubt they would come off when riding. They look just like the wipers on the works forks so it makes the OEM forks appear more like the works Showas they were running in 1978.







2
Tokyo_Tiddler 12/1/2018 2:30pm
12/1/2018 2:30pm
I am in the process of cutting a length of PVC pipe provided by Race Tech to use as a spacer to make up the gap for the much shorter replacement Race Tech fork spring. I have the length I need all figured out and will try to cut with a pipe cutter. Race Tech does not indicate whether the spacer should go on top of the spring near the fork cap or at the bottom of the spring near the dampening rod. Race Tech is closed for the weekend, but trying to get the forks done by tomorrow night.

I figure one of you guys has faced this before installing different length aftermarket springs in vintage bikes. Where do you usually put the spacer? I am leaning towards installing at the bottom of the spring since the ID of the steel washers they provide is too small to go around the nut that tightens against the bottom of the fork cap.

Thanks,
mike
PK97
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PK97 12/1/2018 5:32pm
12/1/2018 5:32pm Edited Date/Time 12/1/2018 5:34pm
The fork wipers look good, can’t remember what I have under my fork boots. Back in the day I worked in a Honda shop and we used the wipers for the GL 1000/1100 Goldwing, they are 37 mm forks as well and fit nicely into the top of the fork. I think that is similar to what I have now. If I was running naked tubes like yours those wipers are the way to go.
Tokyo_Tiddler 12/1/2018 8:01pm
12/1/2018 8:01pm
Thanks Paul.. I will give those a try too and see which look/ fit the best.

I think you just have the oem dust seals that fit inside the slider. Back in 1979, we took off the fork boots and ran that as is which worked fine until you had a mud race.. especially wet sand! .. and then the seals were toast.
Tokyo_Tiddler 12/4/2018 5:27pm
12/4/2018 5:27pm
I talked to Race Tech a 4th time and this time they told me that the 15 weight oil they sent me was wrong and the info is also wrong on the web site. They said I should use 5 weight oil as I had originally suggested. I challenged them on the 15 weight oil the first 3 times I talked to them and they were insistent, but this time I finally got the guy that sets up their vintage suspension and got that mis-info cleared up..

I was also told the spacer should go on top of the spring to limit movement/ interference and that the spacer material and steel washers they sent me in the kit don't work for the CR250. That didn't make me too happy either, but he said it is a generic kit and that no one else offers one for these bikes in his defense. They recommend going to a 3/4" schedule 40 PVC pipe (they supplied 1/2") which will we allow me to use the stock hardware which will fit over the nut on the dampening rod. Just picked up the 3/4"pipe and it does the trick with the oem hardware nicely. The spacer needs to be ~55 to 57mm long with the race Tech springs depending hw much preload you want.

Would anyone like 4 quarts of #15 wt fork oil.. arrrrh!
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RF145
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RF145 12/4/2018 6:16pm
12/4/2018 6:16pm
I could trade you for 7.5 wt if you would like. If it is a touch too stiff, go faster.
PK97
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PK97 12/4/2018 6:37pm
12/4/2018 6:37pm
Mike,

They gave me 5wt when I got my springs. I put the spacer pipe on top of the spring but didn’t question the small diameter pipe as I should have. I assumed they knew what works, when it didn’t look right I should have stopped. Thanks for doing the leg work and getting the answers. I will change mine out and use the 55mm length.
Tokyo_Tiddler 12/4/2018 8:18pm
12/4/2018 8:18pm Edited Date/Time 12/4/2018 8:29pm
RF145 wrote:
I could trade you for 7.5 wt if you would like. If it is a touch too stiff, go faster.
You can have all 4 quarts of the #15 if you can use it, Rich.

I had a bottle of Honda SS-7 5 weight on the shelf so I just got another bottle from Motosport. It is good stuff.

mike
1
Tokyo_Tiddler 12/4/2018 8:27pm
12/4/2018 8:27pm
PK97 wrote:
Mike, They gave me 5wt when I got my springs. I put the spacer pipe on top of the spring but didn’t question the small diameter...
Mike,

They gave me 5wt when I got my springs. I put the spacer pipe on top of the spring but didn’t question the small diameter pipe as I should have. I assumed they knew what works, when it didn’t look right I should have stopped. Thanks for doing the leg work and getting the answers. I will change mine out and use the 55mm length.
Happy to walk you through this Paul so you will know you have done it right. I have been playing with this for several days until I was sure I had it all figured out and was doing it right.. Tried slightly more and slightly less preload to see how much of a difference it made.

If you use the parts that RT gave you, the washer wont go over the nut on the dampening rod that tightens against the fork cap. If you use a bigger washer, it is a bit too big for the narrow 1/2" spacer tubing. All resolved with the 3/4" tubing and the 2 oem washers/ locators.

55mm will be very close to what you need but you should measure just in case. With a cheap digital caliper, I can help you make sure you have the right measurements for your spacer. Always comforting to know it is done right. The RT generic instructions are a pain.

By the way, when you did the Al Baker mod, the hole was very close to the internal rebound/ top out spring in the rod, wasn't it? I am afraid of drilling into the spring.

mike
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RF145
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RF145 12/4/2018 8:50pm
12/4/2018 8:50pm
Tokyo_Tiddler wrote:
You can have all 4 quarts of the #15 if you can use it, Rich. I had a bottle of Honda SS-7 5 weight on the...
You can have all 4 quarts of the #15 if you can use it, Rich.

I had a bottle of Honda SS-7 5 weight on the shelf so I just got another bottle from Motosport. It is good stuff.

mike
Thanks Mike. My older Pre-75 bikes love the heavier wt.
Tokyo_Tiddler 12/6/2018 2:22am
12/6/2018 2:22am
Was all ready to do a finally assembly of the fork and thought I would replace the fork seals with some NOS Honda seals. Big mistake.. I have been at this for 2 days trying to get the seals out. Even protecting with a rag, I have so much pressure on the big screwdriver, I am at the verge of destroying the tops of the tubes and haven't budged either oil seal even after the heating the outside of both tubes with a heat gun.

Looked at you tube for ideas and the only thing I can think of is melting them out. These forks look new inside.. no crude inside at all, but these seals are really wedged in there.

Should have just left them alone.
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PK97 12/6/2018 7:44am
12/6/2018 7:44am
I had the same problem. Had to try and cut the seal in half to pry it, thought I was going to break the leg or gouge the inside. Did wind up with a few marks on the inside.
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MaxPower 12/6/2018 8:32am
12/6/2018 8:32am
I know what would make it closer to the RC bike. Put it in the first turn at Unadilla this June just like the factory did in 78
Tokyo_Tiddler 12/6/2018 9:43am
12/6/2018 9:43am
PK97 wrote:
I had the same problem. Had to try and cut the seal in half to pry it, thought I was going to break the leg or...
I had the same problem. Had to try and cut the seal in half to pry it, thought I was going to break the leg or gouge the inside. Did wind up with a few marks on the inside.
I was thinking of cutting with a dremel tool, but thought the heat to melt the rubber on the outside of the metal part of the oil seal would be safer.
Tokyo_Tiddler 12/6/2018 9:47am
12/6/2018 9:47am
MaxPower wrote:
I know what would make it closer to the RC bike. Put it in the first turn at Unadilla this June just like the factory did...
I know what would make it closer to the RC bike. Put it in the first turn at Unadilla this June just like the factory did in 78
I was there at Unadilla in 1978 Smile I was definitely thinking of taking the bike to Unadilla next year after putting on some cheaper plastic and taping everything up nice to protect from boot rub. The way the bike is coming out, it shouldn't be ridden much.. but to not ride it a few times would kill me also.
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RF145
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RF145 12/6/2018 10:52am
12/6/2018 10:52am
Small wood screws and my slide hammer with vice grips attached Mike.
I can bring this up too.
Tokyo_Tiddler 12/6/2018 5:40pm
12/6/2018 5:40pm
I tried heating it up with a heat gun real good for one more try.. I couldn't even list a corner of the seal. Not sure if these were ever meant to be replaced Smile . I will have to try Richard's secret tool tomorrow.
Tokyo_Tiddler 12/8/2018 4:32pm
12/8/2018 4:32pm Edited Date/Time 12/8/2018 5:35pm
Rich gave it a noble try with his magic tool, but the fork seals were just wedged in there too tightly. Over 4 hours I very carefully cut the metal ring in the seal with a small cutting wheel on a dremel tool. I went little by little to cut a groove rather than cut right through, then grab the metal and tear the metal along the groove until I had relaxed enough outward pressure from the metal ring and could pull the seal out. There was no corrosion and the bore was perfectly clean when I pulled the seal out so the problem was with Honda's tolerances.. way too tight. I did not make any marks inside the seal bore so I was lucky.


I compared the 2 types of seal wipers I found that fit the 37mm forks perfectly. The one on the right is the early 80's Honda GL1000 wiper mentioned by Paul. Which do you think looks better.. I may go with the one on the left.

While I don't mar up the seal bores.. I did mark up the outside a little wrestling with it for 2 days. Even though I used 2-3 layers of thick cloth when prying on the seal, it still market up the top of the pristine tubes as I was applying so much pressure with a big screwdriver. I spent a few hours this morn with sandpaper.. 220 grit then 320 grit then a 3M pad with WD 40 then aluminum polish. Any marks are pretty much undetectable now and look perfect again.. I love working with aluminum.
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PK97
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PK97 12/8/2018 5:15pm
12/8/2018 5:15pm
Nice work slaying the dragon, you did better then me, I lost patience with it.
Tokyo_Tiddler 12/8/2018 5:43pm
12/8/2018 5:43pm Edited Date/Time 12/8/2018 6:01pm
You can tell a lot about a man from looking at his garage, and Richard's garage was no disappoint, yesterday.. he had all the newest tools needed to bring bikes back to their former glory. I thought Rich was mainly a vintage bike guy, but he had a couple of modern bikes there too including a brand new Husky 350 4 stroke. When I first arrived, I saw a garage door open an it was full of vintage motocross bikes, but I was a little confused as it was the wrong address to what Rich told me. Turns out that Rich has his neighbor's garage full of his bikes, too. Rich is a dyed in the wool MXer for sure Woohoo

mike
1
Tokyo_Tiddler 12/24/2018 3:01pm
12/24/2018 3:01pm
Mailman Santa just delivered some presents from a couple of elves based in the UK. I should be able to finish up the bike this week with these parts so watch this space. The Dentons are undoubtedly a critical partner for any top level build and will enthusiastically work with you to make one-off gems. There were actually more parts that came but some went immediately on the bike Smile ...


Here is a really cool shock guard from Stevie to protect the shafts on the Fox Air Shox


The coolest part of all are the HRC replica case screws. I bought a special hollow ground tip screwdriver set from Germany to install these special screws. I wanted to install them right away and got out the impact driver to remove 2 case screws, but after 15 minutes of hammering, I couldn't budge either. Honda could have eliminated untold agony over the decades if they had just used hex head bolts instead of Phillip screws. Will have to figure this out later Sad Maybe an air impact driver.. this either works great or totally destroys the head and really leaves you up shits creek.

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