"Patina" The 1973 CB175 Cafe Racer

[Sonreir]

Just loosen the nut and adjust with a set of needle nose pliers. It shouldn't require much force once the nut is loosened.

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

Just loosen the nut and adjust with a set of needle nose pliers. It shouldn't require much force once the nut is loosened.

Awesome!! Thank you sir.

 

[Texasstar]

Is there a special tool for this square head nut or just use a crescent wrench?

yes to answer your question but we use an 8mm to loosen the tappet but a pair of needle nose to adjust the tappet


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[Sonreir]

Also... sort of on topic... but you can actually calculate the expansion rate of the tappet.

Steel expands at a rate of 0.0000067 inches per degree per inch.

So assuming the tappet is .25" long, your starting temp is 72°F and ending temp is 300°F, you can follow the math:

300 - 72 = 228 (Delta T)

228 * 0.0000067 * .25 = ~0.0004"

Or in otherwords: Next to no expansion at all.

 

[xb33bsa]

Also... sort of on topic... but you can actually calculate the expansion rate of the tappet.

Steel expands at a rate of 0.0000067 inches per degree per inch.

So assuming the tappet is .25" long, your starting temp is 72°F and ending temp is 300°F, you can follow the math:

300 - 72 = 228 (Delta T)

228 * 0.0000067 * .25 = ~0.0004"

Or in otherwords: Next to no expansion at all.

yep when machining parts for a shrink fit i used the expansion coef's pretty often, but translate that to a 4" long valve and you have 6+ thou and for aluminum twice that
the valve and the cylinder head itself is what grow enough to be an issue

 

[Sonreir]

True.

It's not just the tappets that expand. The valve stems also lengthen and help take up that slack.

Kop also mentioned that it's worth taking into account that valves and seats will take up a little more room after a rebuild as everything beds in.

 

[xb33bsa]

Re: "Patina" The 1973 CB175 Cafe Racer

Awesome!! Thank you sir.

they make a tool for it it can be done with needle nose but the correct fitting wrench/tool makes it much easier
when you tighten the jam nut the clearance wants to get bigger you gotta cheat and outguess that change

 

[cxman]

yes there is a proper honda tools set for adjusting the tappets you might even know someone who has it

and i found a set

http://www.ebay.com/itm/Honda-Z50-CT70-SL70-ATC70-XR75-CT110-CB350F-Tappet-Tool-Spanner-and-Adjuster-/121557135787?pt=AU_Motorcycle_Parts_Accessories&hash=item1c4d5eb1ab

you can also just buy a watch winding key in the right size for about 7 bucks i think its a number 8 key but double check

http://www.ebay.com/itm/Hermle-Clock-Winding-Key-Crank-Size-8-NEW-4-1-mm-Chrome-Howard-Miller-Ridgeway-/271020078359?pt=LH_DefaultDomain_0&hash=item3f1a0e3517

 

[Texasstar]

yes there is a proper honda tools set for adjusting the tappets you might even know someone who has it

and i found a set

http://www.ebay.com/itm/Honda-Z50-CT70-SL70-ATC70-XR75-CT110-CB350F-Tappet-Tool-Spanner-and-Adjuster-/121557135787?pt=AU_Motorcycle_Parts_Accessories&hash=item1c4d5eb1ab

you can also just buy a watch winding key in the right size for about 7 bucks i think its a number 8 key but double check

http://www.ebay.com/itm/Hermle-Clock-Winding-Key-Crank-Size-8-NEW-4-1-mm-Chrome-Howard-Miller-Ridgeway-/271020078359?pt=LH_DefaultDomain_0&hash=item3f1a0e3517

thanks cxman that watch winding tool is the ticket 8 bucks is better than 40 bucks
http://www.motionpro.com/motorcycle/partno/08-0073/

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[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

yes there is a proper honda tools set for adjusting the tappets you might even know someone who has it

and i found a set

http://www.ebay.com/itm/Honda-Z50-CT70-SL70-ATC70-XR75-CT110-CB350F-Tappet-Tool-Spanner-and-Adjuster-/121557135787?pt=AU_Motorcycle_Parts_Accessories&hash=item1c4d5eb1ab

you can also just buy a watch winding key in the right size for about 7 bucks i think its a number 8 key but double check

http://www.ebay.com/itm/Hermle-Clock-Winding-Key-Crank-Size-8-NEW-4-1-mm-Chrome-Howard-Miller-Ridgeway-/271020078359?pt=LH_DefaultDomain_0&hash=item3f1a0e3517

That would certainly help. I ended up using needle nose and a tiny wrench. I didn't want to use a socket because I couldn't see the adjuster screw, and on a couple the adjuster wanted to turn if I didn't hold it.

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

Okay!! I adjusted the valves to .003" exhaust and .002 intake, throttle wide open, and got about 119 on the right, and 121 on the left dead cold. I think I'm pretty happy with that. I read around and some forums said 120 is normal for this little twin. What do you all think?

 

[teazer]

That's fine. Could be higher but it isn't, so let's get it ready for spring which will be here before you know it.

This is what we use on stock tappets (valve adjusting screws).

http://www.ebay.com/itm/2218-6-PC-HONDA-YAMAHA-SUZUKI-MOTORCYCLES-VALVE-TAPPET-ADJUSTING-TOOL-KIT-/191504295233

Ours are hollow and broached for a hex key, but that's a secret ;-)

 

[Texasstar]

Re: "Patina" The 1973 CB175 Cafe Racer

Awesome! Are you going to warm it up and check it?


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[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

That's fine. Could be higher but it isn't, so let's get it ready for spring which will be here before you know it.

Woo hoo! I've gotta little something else lined up for spring, but I wanna get this done.

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

Awesome! Are you going to warm it up and check it?


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Yup I'll do that this afternoon and see what it gives me.

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

That's fine. Could be higher but it isn't, so let's get it ready for spring which will be here before you know it.

This is what we use on stock tappets (valve adjusting screws).

http://www.ebay.com/itm/2218-6-PC-HONDA-YAMAHA-SUZUKI-MOTORCYCLES-VALVE-TAPPET-ADJUSTING-TOOL-KIT-/191504295233

Ours are hollow and broached for a hex key, but that's a secret ;-)

Awesome so that knurled pin goes through the "wrench" so you can adjust both at the same time?

 

[1sttimer]

Re: "Patina" The 1973 CB175 Cafe Racer

I'm starting to think that my problem is the fault of a horrible imbalance. I'll focus on that for a while. Couple questions though:

Saw a note from 66sprint in another forum talking about air leaks at the adjustment screw on the top of the carb cap being just as bad an air leaks anywhere else. He said there should be a rubber boot there. Would that cause a problem, as I don't have squat there...

 

[Texasstar]

Re: "Patina" The 1973 CB175 Cafe Racer

The Amal carbs on our Bultacos leak like none other and we found a boot on one carb over the carb for the first time. We are learning about pulling a vacuum on the two stroke to check for leaks. Do you have the black spacer between your carbs and your head?


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[Texasstar]

"New synthetic rubber mounting stubs provide completely live mounts for the 200's dual 18mm Keihin conventional carburetors. Rigidly mounted carburetors often give lean mixtures when a certain engine speed (rpm) matches their natural frequency of vibration. With carefully constructed elastic insulation, this tendency may be "tuned" out as it has been on the CB200."
http://www.motorcyclespecs.co.za/model/Honda/honda_cb200.htm

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[xb33bsa]

Re: "Patina" The 1973 CB175 Cafe Racer

The Amal carbs on our Bultacos leak like none other and we found a boot on one carb over the carb for the first time. We are learning about pulling a vacuum on the two stroke to check for leaks. Do you have the black spacer between your carbs and your head?


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you need to get the engine running and put it through a heat cycle before doing the leak tests
and test it good and warm