"Patina" The 1973 CB175 Cafe Racer

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

If there is too much slack in the cam chain, could that potentially make your timing inaccurate when you time it?

Thinking about that, that may not have been a smart question. When you accelerate, or rotate the crank manually, the slack is removed so timing shouldn't be affected I guess. I was trying to figure our which to adjust first.

 

[xb33bsa]

actually too much slack in the timing chain will mainly cause noise and let the cam flucutate more than it should
flucutate my new word ;D
do the cam chain first always

 

[xb33bsa]

a worn timing chain, stretched out is what happens a tiny bit of wear on each joint x many,this retardatates timing as the cam sprocket,thus cam timing, is further behind the crank rotationaly,than design spec

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

a worn timing chain, stretched out is what happens a tiny bit of wear on each joint x many,this retardatates timing as the cam sprocket,thus cam timing, is further behind the crank rotationaly,than design spec

I'll get out there today and see what kind of slop I have. I'll give you an angle of rotation I can turn the crank before anything moves up top.

 

[xb33bsa]

does yours have a spring loaded lashup tensioner wise?

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

Yeah it's this thing. I read on SOHC that it's almost self adjusting in a way? You loosen the lock nut and the bolt should turn freely.

 

[1sttimer]

This is what the manual says about it....just loosen the nut, let the spring to the work. I guess watch it till it stops moving, hold the bolt with a wrench, tighten the lock nut. Sound right? I need to see how the thing works before I can udnerstnad how this is possible.

 

[1sttimer]

I usually hate websites like this but I feel the guy accurately explains how the process works. The foot of the adjuster pushes down by the spring and rotates the lever around the pin. The sprocket on the back side presses in to tighten the chain. I guess there is no way to manually tighten the chain further than the spring force will allow....and it doesn't seem like screwing in the screw really has any effect at all, so that's good to know because that's something I would do...

http://en.allexperts.com/q/Motorcycle-Repair-837/2011/3/CB175-timing-chain-adjustment.htm

modified with link

 

[xb33bsa]

just be sure you have the slack out of the front fall of the chain you can do this by GENTLY with 2 wrenches hold some very slight force on the cam and crank bolts
you would be holding the crank towards direction of rotation and then some resistence at the cam against rotation
this ensures the chain is snug up front
then let the tensioner loose while at the same time holding snug at the rotating bits
then tighten lock screw before letting loose
this should give you pretty much zero rotational lag
if not,and you have free play , the tensioner is sticking
the system is designed to have zero slack in the chain when cold and even some extrra tension
as the engine warms up the chain grows in length due to thermal expansion at just a bit more than the engine grows
so ideally you have want that zero rotational slack when cold

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

just be sure you have the slack out of the front fall of the chain you can do this by GENTLY with 2 wrenches hold some very slight force on the cam and crank bolts
you would be holding the crank towards direction of rotation and then some resistence at the cam against rotation
this ensures the chain is snug up front
then let the tensioner loose while at the same time holding snug at the rotating bits
then tighten lock screw before letting loose
this should give you pretty much zero rotational lag
if not,and you have free play , the tensioner is sticking
the system is designed to have zero slack in the chain when cold and even some extrra tension
as the engine warms up the chain grows in length due to thermal expansion at just a bit more than the engine grows
so ideally you have want that zero rotational slack when cold

That makes perfect sense. I need three hands so I'll get the lady to help.

I did check the tension and too the eye, any rotation of the crank results in an immediate rotation of the rotor at the cam. Zero lag. I'll do the adjustment you suggested as well.

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

Well I was all set to adjust the cam chain, reached up under the tank for something and ripped the crossover line right at the nipple thing. Gas everywhere, I mean probably a gallon all over the place. Luckily I had some silicone stopper for masking paint that I shoved in the hole and got it stopped, but having to wash the bike after that made me give up for today.

Long story short, I looked back at my eBay order for that tubing and turns out it was for "fuel or air". It was vacuum tubing I had been using on the cross over. No less than Tygon from now on.


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[1sttimer]

TexasStar turned me on to the CB750 airbox boots that look like velocity stacks. They are proven in his dyno runs so I'm looking to get a set of those. In the mean time, I like modeling things so I drew up these stacks that will barely fit into the confined space the frame allows. I'm going to add holes to tap set screw threads, but I'm going to use this model to grow some prototypes on our 3D-printer...SLA. They should be sturdy enough even to use for a run or two. If all checks out, I may move toward getting them machined.

 

[1sttimer]

I also included a little "step" so that the flow is delivered into the throat and not deflected by the flange like some stacks I have seen. I believe Texas Star's Polini stacks are made this way.

 

[1sttimer]

I am ASTOUNDED that a 125cc racing engine can sound like this. Granted it's an abnormal inline 5, but still it's insane.

https://www.youtube.com/watch?v=8MRiPJBFEKA

 

[teazer]

Notice how the tacho needle seems to be directly connected to the throttle. On bikes with any sort of flywheel there's a huge amount of lag. Not so with a racing Honda from back then. Cranks were very different to anything we see on the street. Drop revs and it just dies. They have to be kept at crazy revs just to run.

What an awesome sound

BTW, you might want to try a taper on those stacks for even better flow.

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

Notice how the tacho needle seems to be directly connected to the throttle. On bikes with any sort of flywheel there's a huge amount of lag. Not so with a racing Honda from back then. Cranks were very different to anything we see on the street. Drop revs and it just dies. They have to be kept at crazy revs just to run.

What an awesome sound

BTW, you might want to try a taper on those stacks for even better flow.

It's incredible. I went to the Wiki site that has all of the RC honda race bikes listed and looked at YouTube videos of every one of them.

http://en.m.wikipedia.org/wiki/Honda_RC_series

And also I agree with the taper suggestion. Unfortunately I can't add more than a degree or two without reducing the orifice because the end of the stacks diameter is as large as I can get it without modifying the frame (which I intend to do eventually - live and learn). It will be an iterative process with the SLA which I'm pretty excited about - with hopefully a few dyno runs thrown in.

 

[Texasstar]

Re: "Patina" The 1973 CB175 Cafe Racer

TexasStar turned me on to the CB750 airbox boots that look like velocity stacks. They are proven in his dyno runs so I'm looking to get a set of those. In the mean time, I like modeling things so I drew up these stacks that will barely fit into the confined space the frame allows. I'm going to add holes to tap set screw threads, but I'm going to use this model to grow some prototypes on our 3D-printer...SLA. They should be sturdy enough even to use for a run or two. If all checks out, I may move toward getting them machined.

and Teazer turned us on to the cb750 velocity stacks


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[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

and Teazer turned us on to the cb750 velocity stacks


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Nice! That actually made my day for you guys to pass that along. velocity stacks on these things are quite the frustrating task if the frame is already coated. Flexibility is something I had yet to consider. I have a list of things I will change that will require welding that I'll do over winter, then re-powder

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

As your quote goes..."it's an optimization exercise..."

 

[Texasstar]

Re: "Patina" The 1973 CB175 Cafe Racer

As your quote goes..."it's an optimization exercise..."

that is Teazer's quote also


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