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AHRMA 350 sportsman build (take 2)

172K views 622 replies 63 participants last post by  darksidephoto 
#1 · (Edited)
Hello gents,
So I have wanted to put together a bike to go race AHRMA at willow springs for the annual April race. I live reasonably close ( 2hrs) to Willow, and the idea was just pushed down the priority list by other things and projects. I hooked up with a racer the other day and he inspired me to make this a priority again! He generously offered to help me with set up and parts suggestions.
So here is the goal; build a compliant bike in 90 days, go to track school the day before, and race on April 26th.
I have about 80% of what I need in the garage already, and I will borrowing some parts from my daily rider (rear sets, works shocks, ignition, battery), I already put in an order to Boretech for my pistons, KA slipper, valve guides and gasket set.
Tonight I will start the frame prep by grinding off all the stamped lips that are spot welded so that I can full seam weld the frame. ( pics to follow)
 
#2 ·
Nice!!
Good luck.
I will be following
 
#5 ·
Best of luck!
 
#6 ·
I'm guessing that things like the engine have been removed already and you're working with a bare frame. If so then do section of cutting and welding rather than doing it all at once. That way the frame will stay aligned side to side. Actually cutting those seams off isn't necessary, just a continuous weld along the mating edge will do the trick. Not a pretty though ;)
One other thing I've seen mentioned is adding a cross brace on the lower tubes where the footpeg bar was to stiffen the frame.
 
#7 ·
Guys,
thanks for the well wishes and the tips!

tonight I was able to slip into the garage for about an hour and a half, did some grinding and beating, still a few more hours to go ; maybe on Sunday. Tonight I was able to cut off the center stand lugs, grind off the back bone seam , remove the foot peg bar brackets and trim down the tail section a bit.

My boretech order has not shown up yet; maybe tomorrow. I called and talked to Matt at Racetech , and Mike at Vintage brake, have been emailing back and forth with Buff at THR also, going to buy the lowered 5th gear tomorrow. I hope to have the frame trimmed down this weekend
here are a few pics
 
#15 ·
Here are the plans for the bike..
I will build the motor to the following spec:
motor-
65mm pistons from boretech
NOS head, new valves and guides, head to be ported and port matched
early fat cam with stock springs
lowered 5th gear from THR
KA slipper
tsubaki cam chain
boretech ignition
mikuni VM30 carbs
Ricks stator
barnett clutch

I will take pics of the engine build and share
thanks
Chad
 
#16 ·
you would think that in this age with all the information on the internet; especially since there are a ton of people who swap front ends; that there would be a reference for front end measurements..
1. fork tube size
2. overall fork length
3. fork to stem offset
4. fork spread
5. axle size

I guess all of the internet is devoted to advertising and porn and there must not be enough space left to put something together like this! if anyone knows of anything let me know
thanks
Chad
 
#19 ·
Spent another hour in the garage tonight, "metric mason" was over for dinner, so he helped with the grinding and chopping tonight! Another pile of metal dust and cut off metal bits, frame is going to welder later tonight , he is going to start the full seam welding tomorrow.
 
#20 ·
frame is done being de-tabbed; off to the welder today for full seam welding. My new pistons, bronze valve guides, KA slipper and gasket kit showed up on saturday. I am still waiting for my THR lower 5th gear so that I can start the assembly of the bottom end. I dropped the cylinder/pistons and head off to the machinist saturday and the cylinder will be ready this afternoon. I am getting a port and polish job for the first time; cant wait to see how that feels on the throttle!
 
#21 ·
a quick update,
I was planning on building a mild yet reliable motor for this bike. Not any more... i have been talked into going as far as the budget will allow, so here are the parts I have ordered
THR- PVL ignition
THR- lowered 5th gear
Boretech- megacycle X5 cam
Boretech - timeable cam gear
I will be doing a full race valve train but have yet to decide which and where to buy..
I spent a few hours in the garage last night and the day before getting the cases ready for assembly. This set of cases was from a 69 CL350 , and I previously had them hot tank cleaned and then blasted. I removed the head studs and have tapped all of the threaded holes. You wouldnt believe how much gunk can come out of the threaded holes!!! the cases are sparkly clean (you think) and then pure black coming out of the holes!! haha
I am happy to know these cases are now truly clean and nothing will contaminate the motor.
pictures to follow tonight!
 
#22 ·
darksidephoto,

Good timing (for me at least)! I'm working on a track bike for the upcoming season as well, though you’re doing a lot more performance upgrades. My goal now is to turn a barn find into track bike in the next few months so my goal is to get the bike running with a reliability being paramount and I’ll go from there there. I'll be watching you progress,

Cheers!
 
#24 ·
porting is good with straighten out the intake as your main objective.

polishing is NOT recommended on the intake side of carbureted engines (it reduces swirl which leads to poor fuel atomization which lowers power and makes it difficult to properly tune...polishing is fine on the exhaust side; do the valves and the port. it reduces the amount of carbon build up)

why only 65mm pistons?

with the X-5 cam (I personally prefer the midrange advantage of the 123-40 cam) you should be running larger high compression pistons. you will also need the heavy duty valve springs to prevent float contact over 10K RPM. The 5mm valve stem kit reduces float as well.
be sure to check your valve to piston clearance with any of the race cams as well .060" is minimum clearance.

going up 1mm on the valves adds good power and helps cool the valves, but check current class rules on that one.

the slotted cam sprocket is good, you must degree your cam. expect the cam to be as much as 6 Degrees off in either direction
 
#25 ·
Outobie
thank you for the reply, I believe we are on the same page.
I will be running 67.5 pistons, either the THR or Team Hansen
the valve train will be the 5mm Kibblewhites, still shopping them.
I had previously dropped off a head with new valves, and a cylinder with new 65mm pistons - my machinist is finishing up this work, and now it will go on my bone stock 68 when it needs a rebuild.
I have already dropped another cylinder and will drop another head to be used for the race build (+1 on intake valve/ kibblewhite 5mm full valve train/ KA cut/67.5 bore/ port head)
 
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