XR750

[Herbiev]

Some good advice there. I was always guilty of taking shortcuts to speed things up. Then I realised " What's the hurry. I'm retired"

 

[cyclerider57]

I was able to save the part. The bottom has some damage due to the miss cut but I'll be able to smooth it out to the point it won't be noticeable unless you look specifically for it. I finished the outside machining. I only need to do a little cleanup along the edge. I was debating leaving it as machined but to help with the look of an actual scale of the real thing I will likely give it a bead blasted surface. Right now I'm trying to determine the best order of machining for the cases. I'll probably post a few more pictures of the plastic models and ask for advice on ways to do the work holding of the pieces since they lose most flat surfaces through the machining process and I'll need to make sure the two case halves align properly with pins before the final hole dimensions are bored.

 

[stevehuckss396]

looks good so far.

 

[cyclerider57]

Here are some pictures of the crankcases. If anyone has a best practice on the best method for order of machining or how to best hold the parts I am open to suggestions.

 

[stevehuckss396]

I would try to machine the top photo first. To do the second side I would use the bolt pattern in the big oval to mount it to a plate and them machine the second side. Same with the second piece. Do the bottom photo side first and again mount it to a plate. If the holes in the bosses are through holes for bolts drill under sized and tap them for mounting. After your done drill out the threads to the required size. I have done that a few times.

 

[cyclerider57]

Thanks Steve that's what my initial thoughts were. There are a few surface such as the cylinder mounting locations that I'll need to leave the final cut until they are bolted together but I don't see that being an issue. My real challenge will be at the bottom of the right case where the oil passages are below the cam area. They have cast in valleys in the original case so I'm not sure how to handle that yet. The size and location mean that the standard practice of an angled drilled hole won't cut it. Sorry for the poor picture quality.