-
Enter the April CB750 Supply gift certificate giveaway! It's easy... Click here, post something, and you're entered into the drawing!
750 drag bike in progress
- Thread starter dirtdigger
- Start date
After taking the silver frame apart I decided not to use it. Some welds on there I am not happy with. So I am going to run a stock frame. Just finishing up the new swingarm.
Ended up 10" over stock length and has the wheelie bar mounts where I want them. Still waiting on motor parts
Ended up 10" over stock length and has the wheelie bar mounts where I want them. Still waiting on motor parts
The final crank showed up today so cleaned and checked bearing clearances. Crank now assembled with Carrillo rods ready to into cases. Still waiting on other internals before I can button up the bottom ends in both motors. Slowly coming together...not sure if it is going to get done by spring time. Lot of work goes into building two motors.
Ever wonder how much material gets removed from a cylinder head in a port job?
About a cups worth...plus the piece that found its way into my left eye that needed to be removed! Safety glasses guys!!
This head now flows comparable to the RC head. Finally finished up with the porting and flow testing. Just waiting to finish the rest of the motor to mock up and determine how much I will mill off of it to get the desired compression and for MLS compatibility.
About a cups worth...plus the piece that found its way into my left eye that needed to be removed! Safety glasses guys!!This head now flows comparable to the RC head. Finally finished up with the porting and flow testing. Just waiting to finish the rest of the motor to mock up and determine how much I will mill off of it to get the desired compression and for MLS compatibility.
So after getting over a 5 day long flu...I got one of the bottom ends together. RC crank, new bearings setup to .0018" clearance, undercut trans out of RC motor, new cryo treated primary chain, new heavy duty cam chain. Still waiting on parts and machine work from Cycle X, they are swamped and short on help but need to get these parts back, only have till April when track opens.
Parts rolling in.
Bottom end going together. Lightened crank with Carrillo rods. Undercut tranny gears and a couple of new tranny bearings. Heavy duty primary chains and heavy duty cam chain. All parts and machine work for motors coming from Cycle X. Had an issue on a previous build but after issues from other companies I am now back at Cycle X. Lot of help and information coming from Kenny at Cycle X on these builds.
Bored cylinder done. Wanted to show difference in piston size. Stock is the black small one on the left. On the right is the 72mm MTC piston 12 1/2 :1 compression. Last picture trying to show stock piston in the big bore lol
Bike as it sits waiting for its motor. Fresh paint, mostly wired. Got a little over a month to go before the local track opens....its gonna be tight deadline.
dan1951
CB750 Addict
Your truly an artist with these engines, Hats off to You
Not done yet. Just got my bottom end together the other night. Head is off getting machined down after I figured out how much I needed removed. Then I will have to open up the chambers for the piston crown and cc the chambers to get them equal. Then head assembly and more checking of clearances, then she will be into the frame and fire up. It has taken a lot longer then hoped, seem to be running into one problem after another, either delayed parts shipping or delayed machine work pr wrong parts Waiting on the cylinder for the RC part motor then can finish the top end on that one. I will try my best to get a video with decent sound.
Cylinder head sufaced now for checking piston to head and piston to valve clearances.
Used enough clay to make a preschooler cry.
Used enough clay to make a preschooler cry.
Had some clearance issues that I didn't intend on with these pistons. Clearances ended up a little too tight between the piston and the head, especially by the valve seats. Also had to grind a divot for the spark plug to have enough clearance.
Chamber opened up to match piston diameter and shape...it is pretty close to a full hemi chamber. Need to do some final calculations but should still be in the 12 1/2 to 1 compression range. Now some final polishing of the chambers and final cleaning and I can move on with the final assembly. Crossing my fingers but hoping to have it in the frame this weekend and possibly a first fire up.
Chamber opened up to match piston diameter and shape...it is pretty close to a full hemi chamber. Need to do some final calculations but should still be in the 12 1/2 to 1 compression range. Now some final polishing of the chambers and final cleaning and I can move on with the final assembly. Crossing my fingers but hoping to have it in the frame this weekend and possibly a first fire up.
I think the problem would be that little pond that separates us lol Would love to build 750 motors for others but shipping these heavy monsters around is a no go for almost everyone. If you stick to mild compression then these motors go together with very little problems, its when you try to go more extreme that you start running into problems with fitment issues. I can walk you through needed parts etc when you want to build yourself a bigger motor Bring your bike on over for sturgis one of these years and we will do some motor surgery lol
Bring your bike on over for sturgis one of these years and we will do some motor surgery lol
pistons and cylinder on. Head polished, cleaned and assembled. Head got new 33.5mm superflow intakes and stock size exhaust, new guides, Kibblewhite valve springs. Milled .035" then opened up to the cylinder size. Tried to get compression as high as possible but the amount I ended up taking off made fitting the pistons a pain in the a**.
Head on!! Tomorrow should get the valve train on and get the cam degreed in.
K2750tracy
K2750tracy
Looking good Digger,cant wait too see it in the frame
Hopefully be in and fingers crossed fired up this weekend!
RC 327 cam...she is lumpy. Top end together and degreed in, RC cam, hard welded rocker arms.
Top end buttoned up. Ready to go in the frame.
