CL175 exhaust/tuning/carb

sancho

Active Member
Hey everyone,

This is a repost from my build thread, I thought it might be more appropriate for this section. My build thread:
http://www.dotheton.com/forum/index.php?topic=59122.0

I'm trying to figure out some tuning issues. I've got a feeling that the bike is not running at its best. I got the carbs dialed down as best I can, it purrs like a kitten at idle, revs up pretty good under load, but as for top speed and power its lagging, feels gutless and weak going up hills.

I mean I know its only a 175cc, but I hit 55mph in 5th gear and its damn near close to revving its head off. I get up to 60mph eventually, but the rpms are so high after riding about 20min, the engine gets really hot (pulled up to a light and the motor was steaming).

Also going up moderate hills I get about 25-30mph in 3rd with pretty high rpms. In general, just feels very underpowered and sluggish. Also, I bet the fat tires, 4.00 rear and 3.25 front, are not helping me go faster. (oh and I am 170lb).

I'm guessing the home made baffles (see my build thread) might be restricting the exhaust.

Here is what I have done so far to the engine to make it perform better:

- adjusted the cam chain
- adjusted the valves to spec
- adjusted timing
- cleaned the carbs
- adjusted the float bowl to spec
- synched the carbs to a point where the throttle response is nice, sharp, and even
- dialed the air and idle screws to where it purrs nicely at idle
- installed stock air box filters, nice and tight clamps so no air leak there
- new exhaust crush gasket installed
- Main Jet is at 90
- Slow Jet is at 38
- Jet needle is set to the middle setting
- starts without a choke, rarely needs it
- compression was measured around 135psi both cylinders.

I tried to play around with the float bowl and jet needle setting but all it did was foul the plugs or too lean, no improvement in power.
I tried running without the baffles, just straight pipe, and it ran way worse, absolutely no power and loud as hell, extremely annoying.

So, my plan is to fit the 12" shorty mufflers from dcc with a reducer kit to fit the 35mm(1-3/8") OD pipes.
http://www.dimecitycycles.com/chrome-12-inch-shorty-muffler.html

Hopefully it will reduce the annoying loudness open up the pipes. I would also have to go up on the jets. But at this point will the stock air filter become a restriction? Will pod filters be better with open pipes and jetting up?

Here is the pic of the plugs after running for a few weeks:
LtdsLH3.jpg


I also thought about changing the sprocket tooth ratio to get more top speed, but then the bike feels so underpowered, not sure if that will do any good.

Please chime in with your recommendations and suggestions. I really am clueless when it comes to tuning. Learning as I go here.

Thanks guys!
 
155psi minimum for the 175's. They run all the way down to 90psi but anything under 155 is tear down time
I glanced at your build did you set the float height to 22mm instead of 21mm? It should be 21
Your pipes aren't long enough or tuned with your diy baffles ( the length and shape are important )
Your tyres are too big and slowing you down
 
simo said:
155psi minimum for the 175's. They run all the way down to 90psi but anything under 155 is tear down time
I glanced at your build did you set the float height to 22mm instead of 21mm? It should be 21
Your pipes aren't long enough or tuned with your diy baffles ( the length and shape are important )

I set my float height to 19.5mm per the book

WHBzqx8.png

pi203K5.png


The shop manual is referring to the keihin 20mm carb, which is what I have. Not sure why, because CL's are supposed to have 22mm carbs. But I read somewhere that the 1970 model came with 20mm carbs.

As for compression, I think you might be right, a motor rebuild is a must this winter. I was hoping it was ok because the book called for 142psi, and I had 135, thought close enough. But yeah I will rebuild the motor this winter.

Yeah, I'm gonna ditch the baffles, but before that I have to find some way to reduce the noise, because straight pipes are crazy loud.
 
What 'book'?
My FSM puts the float height at 21mm

I think it's the early CL' s k0 or k3 that have the 22mm venturi but you can't tell unless you measure the bore at the slides all the castings are the same
 

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Here's two that say 21mm
 

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Both the cb/cl 125's and the cb/cl 175's are 21mm
the 160's have the 19.5 as do some of the single carb 125's
 
FYI, these little Honda twins like long exhausts. As you seen, headers alone are horrid for power. Use can use the sorties, but use a piece of pipe to extend them at least to the rear axle.....
 
those copper power sapper deals aren't helping much either :-\ ,might as well shove a potatoe up there
 
xb33bsa said:
those copper power sapper deals aren't helping much either :-\ ,might as well shove a potatoe up there

ha yeah I was gonna shove a carrot but went with the copper for performance hehe
 
arkcom said:
If it's revving high, but not going as fast as it should, your clutch must be slipping.

thats interesting, I haven't touched the clutch yet, only adjusted it, replacement clutch packs seem like they're fairly inexpensive, might go for an upgrade.

this looks promising:
http://maccycles.com/Honda-Clutch-Plates-CL175-all-years-6-pcs-NEW-P2634818.aspx?utm_source=google&utm_medium=Product_Search&utm_campaign=google_base

and this is cheap:
http://www.ebay.com/itm/Barnett-Kevlar-Friction-Plate-for-Clutch-System-301-35-10010-/371145400155?pt=Motorcycles_Parts_Accessories&fits=Model%3ACL175&hash=item5669fd5f5b&vxp=mtr

any thoughts on either?
 
is your clutch slipping ? it is very easy to tell if it is
if it is not, concentrate on what needs fixing
what happened to the stock muffler ?
 
xb33bsa said:
is your clutch slipping ? it is very easy to tell if it is
if it is not, concentrate on what needs fixing
what happened to the stock muffler ?

The stock muffler had a rust hole at the bottom towards the back end, not sure why, but the the pipes were ok, and the clamp that connects the muffler to the pipe had a crack in it. It sat for about 20 years from what I heard from the previous owner.

As for the clutch, as far as I can tell, it seems ok to me. I've adjusted the clutch per manual. With specified clearance on the lever and everything. As I engage from first, I feel it grab it and if I let it go abruptly, it jolts just like I would expect it to.

I've gotten a couple of false neutrals between gears a few times, i think in between 3-4th if I remember correctly. Sometimes, its hard to downshift into first pulling up to lights, after long rides, it just kinda gets stuck on 2nd and I have to tap on it a few times to get it into first going past neutral. But I think thats a gear box issue.
 
shifting the gears has absolutely zero to do with the clutch they are totally seperate functions
you dont even need the clutch disengaged to perform a nearly perfectly smooth, seamless shift on these hondas
the best way to tell if you clutch is slipping is find a hill if you can or not but accelerate hard in 3rd gear at the same time applying the brakes
do it in a part of the power that the brakes really have a tough time overcoming the power
this should make the clutch slip if it is in need of new plates
if the rpms rise and the speed does not the clutch is slipping
 
xb33bsa said:
shifting the gears has absolutely zero to do with the clutch they are totally seperate functions
you dont even need the clutch disengaged to perform a nearly perfectly smooth, seamless shift on these hondas
the best way to tell if you clutch is slipping is find a hill if you can or not but accelerate hard in 3rd gear at the same time applying the brakes
do it in a part of the power that the brakes really have a tough time overcoming the power
this should make the clutch slip if it is in need of new plates
if the rpms rise and the speed does not the clutch is slipping

I will try that, to see if the clutch slips, great tip thanks! There are plenty of hills around where I live.

As for the shifting, I didn't imply that the shifting problems had anything to do with the clutch. I said "I think thats a gear box issue". I was just merely stating the other problems I was having. And will probably lead me to rebuild the motor once snow hits the ground.
 
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