I think I see a new motor build coming....

[dirtdigger]

OK I got a present from Ape today, finally. Everything looks great but it looks like my build will be on hold for a while now. I need to build a good head for this big bore and I just dont have the money to do it right now. But here are some pictures. I compared a set of RC 70mm pistons with my new Wiseco 70mm pistons to show how far things have come in piston technology. I also compared the 70mm with a stock 750 piston just for giggles.

 

[dirtdigger]

I forgot to put in the post I weighed the pistons too. Old RC 70mm piston weighs in at 7 oz. New Wiseco 70mm weighs in at 6 oz. I also weighed a stock 750 piston and it weighed 6 oz. Goes to show how heavy that old stuff is. Lighter pistons make for happier connecting rods and faster revs. Sometimes you gotta love technology.

 

[dirtdigger]

Well newest update. I got a ported F2 head I am going to work on to put on my 970 I still haven't gotten built. I got it really cheap off ebay because it was listed as a K7 head but I had a sneaky suspicion it was a F2 head, and I was right. It is ported but I am going to mill it to get some compression back as my pistons are K pistons. And I have a couple of other trick I need to do to it. But now at least it looks like I may get this motor built this winter!

 

[Travis]

Got to love miss-listed/labeled stuff on ebay. I've found a few good scores myself that way. It used to be much easier many years ago when ebay wasn't so popular.

 

[dirtdigger]

Cylinder sent off to APE to get some machine work done to raise compression and modified to work with my K cylinder. Then I will be calculating my final compression so I can determine base gasket and head gasket thicknesses I want. Then I will finalize the porting and start saving for some good valve springs and retainers...I might get this thing together by spring

 

[grepper]

Got to love miss-listed/labeled stuff on ebay. I've found a few good scores myself that way. It used to be much easier many years ago when ebay wasn't so popular.

Me Too! Scored a K5 rear grab bar (those usually go for $100) because the guy had it listed as a rear turn signal mount, and the main picture was the turn signal. Then I saw the following pictures had the grab bar.

 

[dirtdigger]

Head back from APE. Modified to work with K cylinder oil return and milled to increase compression. Jay did a great job on the oil return modification that they never did before and will be offering as an option now at there shop. You can see the brass sleeve pressed into 4 of the cylinder stud holes that create a oil return. Also had then send me some APE valve springs and they machined me some nice strong and light titanium valve spring retainers to replace the weak stock Honda F2 retainers. Titanium retainers are 5 grams lighter per retainer.

Now waiting for Jay to make me some "special" wrist pins with pressed in aluminum buttons. I have run into a problem the the Cycle X 70mm pistons...the c clip grooves are machined to shallow and the clips do not seat correctly in the pistons. Two of the pistons I couldn't even get assembled because the grooves are too close to the centerline of the piston...couldn't get more then one clip and the wrist pin in the piston...no room for the other clip. Seems there is a manufacturing issue somewhere along the line. Anyway after talking with Wiseco, APE and fed up with Cycle X I am having APE build some custom wrist pins that will do away with the c clips. So now on hold again.

 

[joe p]

Mmmmm.... Shiny stuff!

 

[dirtdigger]

So still not together with this motor. Still waiting on the wrist pins but now they are supposed to be finished Monday. In the mean time even though the head was together I decided to put new bronze guides and Superflow valves in the head. APE supplied the guides which should help reduce the inherent problem with the F2 valve guide issue. The valves are Cycle X undercut valves because well you cant have to many cool parts to help make more power. Guides went in well with the exception of one that fit loose so had to order an oversize guide. Decided to buy my own cutters to do my own valve jobs from here on out. I like to have control of as much as possible in my motors so this is one less thing I have to worry about a machine shop not screwing up.

 

[dan1951]

That is going to be one BADA-- bike when Your finished, Are there any plans of having it on a dyno? I would love to see the H.P. Torque ratio on that monster.

 

[dirtdigger]

Problem is nobody has a bike dyno around these parts except for during the ralley in August. If I have time etc. I will try to have a dyno run done.

 

[Stabler]

Mmmmmmm - motor porn. I love it.

 

[dirtdigger]

Finally....after months of gathering parts and machine work and trial fitting and error, the 970 runs.

Straight out it is much stronger then the 836 it replaces, the 180 rear tire doesn't stand a chance. Now comes for some fine tuning with the carbs etc.

Next up...I need to get some bigger carbs to take full advantage of this cylinder head, wish I still had those Webers my dad sold years ago

 

[dan1951]

Being patient paid off, That Badboy looks great.

 

[dirtdigger]

I ended up running a Megacycle 125-75 cam that I had laying on the shelf. I was going to run the Web 63b that I had been running in the 836 motor but as it turns out it had too much duration for the big valves of the F2 head causing the valves to get within .010" on overlap...way to close. The 125-75 has a little less duration but more lift and it made the clearances more happy, and that is why you never take any ones word for it when they say it should fit or it does fit. I always test fit and measure every clearance when using performance parts...nothing is a drop in and dont assume it will fit

 

[motogtp]

I would love to hear a video of that thing running!

 

[Stabler]

soo.. New carbs eh? Wadda ya doing with them K7-K8 intake rubbers then?

 

[dirtdigger]

Its going to be a while before the new carbs happen. They want so dang much money for carbs Mine are F2 rubbers...they are bigger then any of the K

 

[Stabler]

F2 rubbers will fit mine since I don't have a stock airbox in the way behind the carbs. F2's are only longer from what I know.. But as you wrote. And I'm in a hurry so I'll keep looking elsewhere.
Good to hear you got it running though!

 

[dirtdigger]

I would love to hear a video of that thing running!

In all honesty it doesn't sound like most people would think. It is loud but the large displacement really calms down the rough idle you would think it would have with the cam. The 836 had a lot rougher idle mostly due to the fact the cam in that one had more duration then the current one in the 970 motor. If I can get a decent video with good sound I will post it.