Saving a 1980 750 twin.

school and work have been killing me, no time for projects. I needed an easy win so I found a little time to hop on the lathe and turn up a tach delete.

Got a start on the stainless header today. Exhaust flanges next.

that should work nicely!

leon

Im planning out my header design and want to run over it here for my own clarity and to get the opinions of some knowledgeable folks here.
Its going to be a stock motor with the stock carbs and airbox. (for the time being)

The stock header ID is 1.28" Since i figure this is probably the optimal size for good velocity I didn't want to go bigger but the tube i have found comes in 1.5" with a .065 wall which puts me at 1.37" ID this is only 0.1" diameter increase so it shouldn't effect it much but will probably move the powerband up slightly in the RPM range.

From what I understand it is good to have a larger exhaust diameter than exhaust port to create a step to help prevent reversion. The exhaust port is 1.37". I don't want to go bigger because it would kill the exhaust velocity, so i have been scheming on ways to help prevent reversion. I put a internal chamfer on my spigots to mimic the factory header design where the two tubes are welded together. I figure a small step like this may help with reversion.
I have also been reading about anti-reversion inserts and am contemplating adding them. Does anyone have any experience with them? i have read about them over at the XS650 forums and a guy that races one swears by them. Apparently they don't significantly increase power but help with throttle response and torque.
Im asking this because it will change how I design the exhaust flanges. If i do the anti-reversion inserts the exhaust collar will have to fit on from the head side and use a ring to hold the exhaust in place much like the factory. If i don't use the AR inserts the collars will simply slide on from the collector end. I drew up a cutaway real quick to show what I mean.

Thoughts?

A bit unrelated to the question, but down at the collector a goilet is recommended. Have you looked into how they are designed? Some are shown in the link below. Ed

www.google.com/search?q=exhaust+goilet&b...wBQKHaw5DToQ_AUIBygC

I didn't know that is what those are called. this ts a twin so the pipes just merge.

DOH! I got so interested in the theory I overlooked the fact that you're working on a twin! :blush: Ed

Got a start on the exhaust collars

Retaining rings done

Turned up a bunch of bungs. Stainless on the left for the 1000 exhaust hanger, and mild on the right for the passenger foot peg mounts and the exhaust hanger for the 750. Chipping away...

after you machined them,
tell me you pulled your t-shirt up over your head and ran around saying



i can never machine up bungs without at least a couple beavis and butthead jokes
jokin aside nice work they should end up as nice details.

leon

haha, i haven't seen that movie in ages. my brother was obsessed with B&B when we were kids