Yes.  It is getting time to get some pressure behind the rings.  It has had around four heat cycles and maybe 30 miles under its belt.
Time for 3/4 throttle with full throttle every now and again and let it rev out in 5th.  Six is too high because i geared it for the road.  1st was stupid low for the road.

I am absolutely paranoid of the thing.  It is cursed.
Never really bothered with break in before.  Just used to ride normally but avoiding prolonged full throttle.
 

Had the opportunity to give it a bit more of a run this morning. I let it rev through the gears and in top kept it at 5000 rpm. This is around 3/4 throttle and 50mph because of the road gearing. It revs through the gears nice and cleanly.

I am a tooth up on the front sprocket to make top a better prospect for roadwork and bottom better for pulling away.

I am running premix at 32:1 in the tank and whatever the pump is contributing. I am thinking of running premix only. One less thing to be paranoid about.

I have absolutely no faith in that pump continuing to deliver, despite checking output over 200 pump strokes, and have absolutely no reason to doubt it, yet I do.
It will unexpectedly stop delivering at some point and ruin the engine. It is the curse of this bike.

Indeed, I have no faith in the entire machine. It has been so much of a hassle, I cannot enjoy it anymore.
You would not believe the money, care and attention that has gone into building it, yet it steadfastly refuses to co operate.

The test ride went well and the vibration, while still there is getting less. Still a tingle through the pegs at 5000 rpm, but not enough at the bars to blur the mirrors.

Now the piston is not clattering away, I notice quite a bit of clutch rattle when the motor is hot and idling. It does not do it when cold and goes away when the clutch is pulled in. I will need to pull the cover and have a look.  I am thinking loose clutch basket rivets.... If so, could this be the cause of the vibration?

To cap it all, it looks like the new headlamp bulb just blew...


I have had enough of the PoS. Thinking of cutting my losses and selling it. Maybe the next owner will have more luck.

Don't give up yet, she's not quite perfect but getting very close. Did the other bulbs blow too or maybe was just vibration, 'sorry shouldn't say that word', does it have a regulator to save the bulbs if the main one blows. Might be just a cheapy bulb--filament & it fell off. Ya never know where bulbs are made these days.

I am with RT, don't give up unless it feels like being on vacation with your mother-in-law!

Well what a great holiday this has been.  Rain every day and a mild dose of covid to top it off.  Breathless, wheezy, clammy, really annoying cough fatigued and no taste.

Still, advice taken on board.  Stopped sulking and pulled the clutch.

I was hoping for 1 scenario - clutch center nut come loose.

Not wanting scenario 2.  Clutch basket rivets loose and movement between primary gear and basket.

Absolutely dreading scenario 3.  Mainshaft bearing breaking up at the clutch side.

Drain oil and inspect for debris.  Some friction material, but thankfully no metal filings.


​​​​​​Inspect center nut.  Still tight.  Damn.


Smoking gun.  Clutch basket rivets still tight, but I assume there are damping rubbers in there.  If so, they have gone hard and gradually been compressed under the heat and torque from the engine.  They are no longer elastic.
When I built the clutch there was a tiny amount of play, certainly not the two to three milimeters it has now, between the gear and the basket.  The basket looked to be as new.
This is the rattle I am suddenly hearing at idle. 
Whether it was there before but covered up by the clatter of the duff rebore, i dunno.  I only just started noticing it.

I heard somewhere that this is a very common state of affairs and placing a tight,  thick O ring in the recess between the gear and the basket will dampen out the rattle.  Making a big thick o ring is no problem.

Any one heard of this "fix" and if it works, how thick do I need to make one?  Otherwise it is a NOS basket if I can find one and I am done spending big on this bike.

Smoking gun.  Rotary play twixt gear and basket.  No end float or other play.  Rivets are tight.



​​​​​Original pic during build.  O ring would fit in small channel between gear and basket.

After several hours of hearsay, chasing down leads and blind alleys,I have managed to come across some new damper rubbers.

Amazing, I never knew you could get them separate.  This seems the way to go.

Seems I just need to drill off the rivet heads, tap out the holes 6mm with a 6x1mm tap, replace the rubbers and use the supplied bolts instead of the rivets.

If it still rattles just fit the genuine yamaha fat rubber ring in the V between gear & basket.
#2 i found on a "74 DT175.
Probably still fit in, just stretches over the gear & 'in'.
Damps any movement.
Cool what ya doing though replacing cush rubbers.
If ya worried about indicernable noises ya can't fully trace, then leave the basket & cover off & wrap a rope around the flywheel & pull start it--then all will be revealed--or not.
Forgot the link sorry.
www.partzilla.com/catalog/yamaha/motorcycle/1974/dt175a/clutch

If you fit the button head allen bolts, the clutch centre may contact the heads. Rivets of the correct size are cheap and easily available.

The damper rubbers tend to go hard over the years, and this needs to be checked, if the ones you have are NOS.

Drive fingers on the clutch basket often crack if there is a lot of play between the basket and drive gear, and must be welded before the basket is rebuilt.

At this stage, it would be a good idea to strip the motor completely and rebuild it properly.

Wow RT. I thought the O ring thing was a quick bodge, not a genuine Yamaha "solution".

I looked in my parts book and it is not there, so the old geezer did not take it off and lose it.

Clutch rubbers on the way from Germany so I will take the basket to work and get the machine shop to drill the rivets. Far better they do it than I at home with a hand drill.

I will also get them to countersink the holes in the cover plate and instead of fitting those button headed screws, fit countersunk screws to better keep everything aligned and more importantly, balanced.

I will also make and fit a o ring as per your parts drawing. I am a great believer in belt and braces.

Later models of the 175 (1976 on) have a smaller clutch gear so the earlier o-ring doesn't fit and wasn't used.