Higher gearing for 175

[ranton_rambler]

Second question today.
I find my little 175 is keen enough but seems to run out of puff at about 55mph. It will eventually get to 65/70mph on a suitable road.
First gear seems really low.
I have standard sprockets at the moment, which means 15T on front.
Is there any experience of increasing gearing?
Ian

[George]

Hi Ian The 175TS is a touring bike and listed as a top speed of 68MPH. My experience of other Italian bikes show that top speed is indicated with small skinny rider crouched over handlebars. no head wind and a long run.
To get the most on little bikes everything needs to be spot on and perhaps best to check settings first. Sorry if I am stating the obvious sometimes we forget the simple things.
Have you got standard piston and cam shaft. Did you check valve timing when restoring bike.
Check points gap. Check Ignition static, check full advance with strobe. Check spark plug gap. Check valve tappet clearance.
At throttle wide open main jet supplies fuel. If you ease off the wide open throttle do you get a brief increase in power / revs.
What type of air filter do you have and is it clean. Perhaps a full throttle plug chop will show if lean or rich.
Worth checking rear sprocket size is standard, my parts catalogue shows 44 teeth.
If you increase size of engine sprocket you should get an increase in top speed at the expense of slower acceleration and slight drop in power at low revs, you may have to hold intermediate gears a bit longer especially going uphill. I would try an increase of one tooth first if all working then decide if it's worth increasing by 2 teeth. Would be good if you could borrow sprocket before you buy. Mine are 15 and 44 same as yours.
If all this makes no difference and you have a need for speed wheel the Guzzi out

[ranton_rambler]

Hello George.
I’m fairly happy with motor, which is basically standard apart from the Sport piston. I think the performance at high rpm is limited by the breathing.
I did quite a few miles in company with other 175cc bikes on the 3 Moors Run and found that mine could keep pace with the others (Morini, Gilera, MV) although mine maintained speed uphill better.
I’ve checked max speed with GPS and have seen 65mph, which is about 70mph according to the speedometer.
I don’t think I want to go faster, just a reduction in engine speed when keeping up with traffic. The motor sweet spot seems to be at about 45-50mph which is a bit slow on main roads. It will sit at 50-55mph but seems a bit cruel to the motor.
I’ll order a 16T and try.
Incidentally, my sprockets are 15/46 but am on 18” wheels. I think yours are 17”?
Ian

[George]

Hi Ian I think 175ts rear should be 44 teeth with 18 inch wheels so this could be your problem.

[ranton_rambler]

Interesting, my parts book says 15/46, so as far as I know it’s standard.
16/46 would be slightly higher gearing than 15/44 so worth a try. Rear sprocket is more difficult to change as I have the unusual 136mm brake with 4-peg sprocket. I haven’t found anyone that stocks those yet, so when it’s time to replace I’ll probably have to get something made.

[George]

That is interesting. You may recall that mine is a Mototrans 175TS and my Italian/ English parts list shows 15T - 44T. A 125 engine has been fitted at some time.
Standard 15T - 44T gives ratio of 2.93 to 1
Your 15 - 46 gives ratio of 3.06 to 1
Proposed 16 - 46 gives ratio of 2.87 to 1
This would give lower engine revs for given road speed.
I would like to know how it turns out

[ranton_rambler]

Maybe primary gearing varies between models too? I’ll count my teeth if I take the left cover off.
Will update with feedback, but might be a while as I’m doing a few other jobs on it too, and then I might not fancy riding in the cold.

[ranton_rambler]

Counted my primary gear teeth - 24 x 60.
According to Mick Walker this is correct for a 175.