CB350 Built by a teen (Weld Now, Grind Later)

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

yes, bore-tech... ahh, I knew that about piston skirt vs crown... meh, we all make mistakes I suppose. makes sense about having low dome vs high dome (plus I figure less material on piston=lighter piston) but the main reason I went with bore-tech is for the deeper valve cutouts for a bigger cam down the road.
Since the edge is already level, and the local machinist can't skim less then 30 thousandths (he says his machinery isn't accurate enough/its not worth the time (cost)?) I think I'm just going to leave it as is and order a gasket thats .016" thick. I figure thinner= better (better seal? though I'm considering heat transfer may make up the difference?) and .016" isn't very much to take off the compression ratio. confirmation?

anyway, heres some pics of the swingarm work and the brake with the mesh behind it. Couldn't work on it at all today or yesterday (yesterday was with girlfriend doing boring things, thankfully she made it up by doing fun things that night) (today was spent building up my fathers bicycle from the frame up, he now has a sick 8 speed hybrid that is a fricken BLAST around the city, my gift to him for fathers day) BUT... my tracy body came in! fits better then I thought it would, I'm seriously considering just cutting out the tunnel a bit in the back and mudding in a new wider piece and it will fit almost perfect... No pics yet, and going off to my rutgers orientation for the next two days so I won't get to work on it at all/take pics.



Needs some finishing work and body filler...

welded the drum brake stay back in place... not a bad weld considering my experience/ using an arc welder...

OOOH, Mesh... that automatically means I'm hardcore... without those holes, my brakes would melt instantly. without that mesh, well, it wouldn't look as cool.

using the swingarm I got my rear wheel within .01" of true side to side and up and down... thats less then half a MM for you metric folk (yay metric system!). used a dial caliper and my sweet motorcycle spoke wrench set. any of you who bitch you need a truing stand just need to get some skillz 8)

 

[t71ford]

Re: CB350 Built by a teen (Millin' and billdin')


Whoa, is it just me, or does there appear to be progress in this thread ;D

The brake cover holes and mesh look really nice!

 

[crazypj]

Re: CB350 Built by a teen (Millin' and billdin')

Yep, 0.016" Base Gasket and 0.024" head gasket if he lists one, that will put you at 0.040" squish (or quench)
Both mean the same but squish is usually used for two strokes and quench for four strokes
It's piston to head clearance ;D
0.032" is probably too small and you could have piston hitting head at high rpm, weird things happen at 12,000

 

[haplo_84]

Re: CB350 Built by a teen (Millin' and billdin')

yeah that whole metal stretching thing cause of heat and momentum doesn't sound like a big deal because you think its minimal until shit goes wrong at those speeds.

 

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

hmmm... 12,000 rpm?

shit PJ... you gave me a goal for my second build

thanks to T71 for the compliment

in other news, talked to AD Pete (same guy who helped me weld my swingarm brace) and hes going to help me cut out the channel of my tracy body and paste in a new one. I think i'm ditching my plans of using it as a faux tank since the body is so close to fitting and would be less shit i have to bolt on...

 

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

picked up my head today, looks like a good job. just sent an email to lani at copper gaskets, getting a .016 base gasket and a .021 head gasket for a total quench of .037", as per PJ's recommendation.

will be mounting tires today and doing other nick nacks...

 

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

damn tube punctured while being mounted. fucker... hate it when that happens. now I need to get another tube >,>

 

[cafePete]

Re: CB350 Built by a teen (Millin' and billdin')

damn tube punctured while being mounted. fucker... hate it when that happens. now I need to get another tube >,>

Happened twice to me with the rear tire, worst part was that I ran out of tubes till the next day... ;D

 

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

i think the main issue was the tire was cold. tomorrow ill leave it out in the sun so it warms up and gets more pliable

 

[teazer]

Re: CB350 Built by a teen (Millin' and billdin')

If possible it's better to machine head to reduce combustion chamber volume and fit lower dome pistons

PJ. Would you please stop giving away all the secrets. ;-)

That's exactly what I do - keep the crown low as you can while maximizing CR. You get faster burn, better power and way better power out of corners. I understand why pistons are sold with such terrible crown shapes, but there is more than one way to get to the answer.

 

[crazypj]

Re: CB350 Built by a teen (Millin' and billdin')

damn tube punctured while being mounted. fucker... hate it when that happens. now I need to get another tube >,>

Just bad technique, fitting rubber gets easier with experience ;D

PJ. Would you please stop giving away all the secrets. ;-)

That's exactly what I do - keep the crown low as you can while maximizing CR. You get faster burn, better power and way better power out of corners. I understand why pistons are sold with such terrible crown shapes, but there is more than one way to get to the answer.

I guess you saw my post on 'the other site' 8)
I thought everybody knew that?
We know there are other reasons as well, won't go into that though.
With the right cam you can probably run 14:1 CR on pump gas (don't try this at home folks, Teazer and I are 'Perfesserniuls' ;D )

 

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

heh... had a family barbecue all day... turns out that a friend of my uncles is a professional welder...

well, thats an understatement. hes more or less as good as they get. welded for over 50 years professionally, and is now an instructor at a welding place here in the city. hes giving me some pointers on arc welding on wednesday, and in time I hope he can teach me TIG. the guy can sow together metal damn well... been doing it since he was 12 apparently. woohoo!

 

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

Just bad technique, fitting rubber gets easier with experience ;D

I honestly can't figure out how it punctured... I was so damn careful to not pinch the tube, and felt with my fingers the place where the tire lever was going before I put it there. must have pinched in the last moments of mounting... sigh...

 

[t71ford]

Re: CB350 Built by a teen (Millin' and billdin')

There you have it, folks! By David's own admission, he has a 'pinched tube'!

 

[crazypj]

Re: CB350 Built by a teen (Millin' and billdin')

You had some air in tube?
I don't usually take tyre levers further than 90 degrees to rim, going further is when you pinch tubes

 

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

put some air in tube so it holds its form when putting it in (so it doesn't fold over on itself/twist around). all air was let out once tube was in.

90 degrees eh? and then you just push the tire down on top I assume? I tried that initially, but the tire was such a B**** that it took a bit more to flip it in. I'm thinking coldish tire made it a lot harder...

I've changed enough tires and fixed enough flats on bicycles to know how the process is supposed to go. just a bit more "convincing" is necessary with the moto. tire...

 

[crazypj]

Re: CB350 Built by a teen (Millin' and billdin')

Make sure you have tyre bead in the spoke well opposite (you know from bicycles)
Personally, I find it easier to kneel on tyre to hold it into rim and work 180 degrees away over the rim.
Was teaching Brendon this evening, still can't do much with arm
'We' fitted rear rim to front, he noticed a difference instantly, even with the same 90/90 tyre (off one wheel and onto the other)
I haven't shown him how to balance it yet, was feeling sick so had to lie down.

 

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

Makes sense, I tried leaning on it, I'm too light a guy I suppose. If I screw up the second time, I have to stop being retarded and do it right.

 

[crazypj]

Re: CB350 Built by a teen (Millin' and billdin')

Don't let all the air out, tube needs to hold it's shape.
you can let a bit at a time out as tyre gets further onto rim. use a dish soap/water mix to lube stuff if you don't have proper tyre lube
De-burr and polish tyre levers as well and dip them in solution

 

[Rocan]

Re: CB350 Built by a teen (Millin' and billdin')

polish my tire levers... oh god, if I start with one tool, I'll have to do them all!