Vintage Dirt Bike Q & A

If you're going to spilt the case I'll offer a few comments.

1) Buy some engine cleaner and clean the outside of the engine thoroughly before you start

2) Buy or make a case splitter. This is similar to a flywheel puller but it bolts over the rotor side of the crankshaft with 2 bolts. You may have noticed the extra threaded holes in the case. After all the screws are removed you apply pressure to the crank and the case comes apart. Never pry the seam with a screwdriver and don’t beat on the crank with a hammer.

3) Buy new correct large size bits for your impact driver. Bought mine at Sears. Make sure you have an impact driver. Once the heads are stripped it's too late.

4) You can leave the Clutch basket in place if you are absolutely sure the bearings are ok. If you aren't sure, now is the time to change them. Remove the nut from the crank with a pneumatic wrench. You can twist the basket to remove the gear from the crank. Threads are standard direction. Righty Tighty, Lefty Losey.

5) Have a nice clean work area. I covered my workbench with some extra linoleum.

6) Order the gasket set and seals before hand. Got my gasket set on ebay and a seal kit from http://www.elsinores.com/ same seals as the 73 CR-250. Just missing the tachometer.

7) Buy some chemical gasket remover and an aluminum tool so you don’t scratch the surface. Notice how clean mine are in the picture.

7) Have plenty of cold beer on hand. I took my time and spent an hour here and there. Very rewarding once it’s all done.

I’m not sure what those thing are with the teeth either but I did try to leave them in place so they wouldn’t get lost. If your bike has any problems shifting you may want to inspect them closely.

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74 MT-250
06 Husky TE-450

Will the seal kit for the 73 cr250 also work on a 75 mt250?

from what I understand 74-76 MT should be the same.

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74 MT-250
06 Husky TE-450

Jake, Thanks for all the tips. The beer supply is good but I will have to invest in some tools. Did you order the full seal and bearing kit, just the crankcase seals, or somewhere in between?

What gasket remover do you recommend, and what prep do you do on new gaskets to make them easier to remove next time round? Who makes the gasket removal tool? Thanks.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Michael:

First I used the aluminum tool, then chemical, then the tool. Even with the soft head on the tool you must still be careful. There is no brand name on it but I bought it at an auto supply store years ago. As for the gasket remover it was Permatex spray gasket remover 80646. I tried to aim very carefully so it wouldn't hit the outside finish. I immediately wiped off the excess. For the lower case I sprayed both sides of each gasket with Permatex High Tach Spray-A-Gasket sealant 80064. The head gasket and the base gasket I sprayed with Permatax Copper Spray-A-Gasket 80697. The Spray-A-Gasket can be removed with denatured alcohol. Unfortunately the Honda shop manual doesn’t address any of this. I’m not saying that I chose the correct products but they worked for me.

Here is a picture of the case splitter that I made from and old piece of angle iron with a nut tacked on. The threaded shaft was from a pulley remover. Also shows the gasket removal tool.

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74 MT-250
06 Husky TE-450

coleman4130

My bearings were tight so I didn't bother. I believe you would need a press for that task. I did replace the 5 seals. The box from Vintage Elsinores is marked with number 73742SK.

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74 MT-250
06 Husky TE-450

Jake I made the same tool years ago when my 74 cr was 2 yrs old, I had bent a shift fork and I think in the original owners manual they must have shown a picture of this tool, as I don't think I came up with it myself. I never use sealer on my gaskets and have in fact used grease on them if I know I will have to take it apart again. I beleve the reason Honda does not mention sealers is that they dont use them. I've put together alot of 4 stroke z50 and ct70 motors and have never had a leaker. Too many times people use too much sealer on these ohc engines and clog up the small oil passages that feed the camshaft, wrecking the head and valve train.Not a problem on these motors tho, but your better off making sure your gasket surfaces are super clean.I use a single edge razor blade to clean mine.When you go to put the crank into the case, I have had good results warming the cases 1st and the crank will drop right in. And if you round out the head of a phillips head screw in the case, I just get a drill bit that is about the same size or a little larger than the screw and drill off the head . Then when you get the cases apart you can grab on to what is left with a vice grip and they come right out. I think that as you hit the impact driver with the hammer it must bind the head on the case plus the fact that the screw is still under tension the head then strips.On one of my last motors I just drilled them all out rather than mess with them. Good luck Gary

Jake, you suggested leaving the clutch basket in place, which sounds like a good idea! I have removed the main crankshaft bolt (I should try to post a picture of the penny that did the trick!) but the gear is obstructed by the basket. I apologize if this is a stupid question but can a I split the cases with the gear in place and catch it when the crankshaft slips through and away?

This is all great information. We should start a MT rebuild / hop-up topic in the Reference section. Not a Q&A, just tips, what's compatible, etc.

Thanks!

Gary:

Can't remember where I picked up the gasket sealer habit. I know we used form-a-gasket on everything but head gaskets in that 1 year of highshool auto shop I had in 74. Messy stuff. The products I used on this last rebuild (June 2003) would probably prevents sticking and make the next job easier.

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74 MT-250
06 Husky TE-450

coleman4130

Steps to a rebuild would be a great topic. I started looking through some more of my pictures and I noticed that it is in fact a bolt that holds the gear on, not a nut. I will have to correct my earlier post. If my memory serves me right you should be able to rotate the basket and the gear will come off. Maybe you have to pull out the crank at the same time if there isn't clearance. And yes, you can split the case with the gear on. I would remove the bolt first. Let me know.

Here’s the proof.

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74 MT-250
06 Husky TE-450