I do want to keep the bike unmolested and to keep the lights working. It is dark at 6pm here this time of year and a good brake light prevents rear end collisions. Some of my riding buddies are CRAZY, you know?
No horn, no battery and the stem sticker says "competition only" so I am guessing I will not be able to register for the road:
(last digits fudged) Generally the DOT will not allow vehicles with this on the highway. We do register them for off-road.
I have road registered non-batteried off-road bikes before. The orange KTM is mine.
I did opt to install a tiny battery and DC full wave rectifier circuit for the horn, signals and to keep the head and tail light on if I was to drop the bike on a dark rainy night road. It also allowed me to use bright 20w brake and signal lights that would work engine on/off or low rpm. I still used the AC for the headlight. The voltage regulator is just a 14.3v voltage limiter (shunt). This all adds weight and complexity to what was originally a very simple bike. No plans to do this to the TY175, although it sounds like a voltage regulator might be in order?
I've done some work on Yamaha Blasters, KTM and other 2 strokes and found there is much more than air restriction going on with the airbox. I've found many high flow aftermarket intake airboxs lose power, as do many of the "common sense" mods that are suggested on the internet. One guy does it without testing, reports on it or posts cool pictures and it takes off like wild fire.
As a rule, intake systems should maintain a steady cross sectional area from port to filterbox with some gradual decrease as it approaches the port. A slight coning (or trumpeting) as the intake port enters the airbox is preferable to broaden the affected rpm range. Longer favours lower rpm, shorter favours higher rpm. There are formulas (read up Gordon Jennings, Gordon Blair, A Graham Bell) but experimentation is still needed, especially with harmonics and Helmholtz box factors. The box volume itself is important also, and the same, bigger favours lower rpm.
Often where you gain power at one end, you lose it at another. I have made long intakes that gave tractor like low rpm power but hurt top rpm output. Most of the time I was looking for mid-range to max, which I gather may not be what a Trials needs?
All this said, to my eye the TY175 airbox does not look too bad, and the filter has ample area for the carb. An airbox lid is important for resonance, but if you feel it is restrictive, test with it removed.
Ah, testing! That is the rub. Without a dynometer, I find speed testing on a hill the most repeatable. Fit a speedometer, digital bicycle speedos are cheap, accurate and easily adapted. Find a long steep hill and establish 2 markers on it. Pick a gear, enter at a fixed low rpm and give it WOT at the first marker. Record your speed at the top marker. This is you baseline. Now you will know if any mod you do makes more power or less.
The carb o ring is available from Yamaha,I found one in my tool box that worked.there are two o rings in the carb replace them both.
the rear sprocket is dished ,it is the same as the one used on the tw200 ,only tw is steel not alum ...you can get them aftermarket in 51t, cheap Front sprocket is 12 teeth Same as xt/dt Allot of different models and brands use that spline size 428 chain ..just service the forks New seals and oil they are soft anyway
dont worry too much about tires now ,new tubes and if they hold air ....get some time on it ..then get tires
common issues are the kick start ratchet mech and worn shift lever cover plate /forks and difficult shifting.
your bike looks good ,you have fenders,nice tank,silencer...even both lights....do you have both switches and is your oil pump still there?
think you would have a difficult time getting a plate and would be strange to ride on the road.... my opinion.....most aftermarket throttle cables do not have a oil pump cable...so you know
model code is 525 They are super easy to work on
I've bought a generic "O"ring set, but haven't tried to see if one fits yet.
Found an OEM air filter on Partzilla, ordered
I do have the oil pump, but it is not on the bike, it does have the split cable, I ordered a single cable
It is a 1978 with matching engine# and I have a 1979 frame as well, no other spares
My switches are banged up, button broken. Haven't started, don't know if work
The pipe and silencer are very heavy, I suspect carboned up. How to clean and repack?
Thanks Scifi, Section and Tony - this has been so helpful!
I swapped the o-ring on the main nozzle tonight - still leaks so that's off the list (and it did fit because I can feel the resistance when I put the bowl on).
You can see the scoring on the needle - I'm really hoping that's the cause of my leak. I found a place in the US (jetsrus) that stocks parts for the Mikuni VM26SS - so might get lucky going that route.
I'm fortunate that my bike came with a well used owners manual - it's quite detailed and ha been very helpful.
I am new to the TY, but not to old bikes. The needle seat will often build up a coat of varnish. Try cleaning it up with a "Q"tip and a small dab of toothpaste. Swirl it around and wash it up before assemble. Usually works.
1978 TY175 overhaul
in Yamaha
Posted · Edited by sbest
I do want to keep the bike unmolested and to keep the lights working. It is dark at 6pm here this time of year and a good brake light prevents rear end collisions. Some of my riding buddies are CRAZY, you know?
No horn, no battery and the stem sticker says "competition only" so I am guessing I will not be able to register for the road:
(last digits fudged) Generally the DOT will not allow vehicles with this on the highway. We do register them for off-road.
I have road registered non-batteried off-road bikes before. The orange KTM is mine.
I did opt to install a tiny battery and DC full wave rectifier circuit for the horn, signals and to keep the head and tail light on if I was to drop the bike on a dark rainy night road. It also allowed me to use bright 20w brake and signal lights that would work engine on/off or low rpm. I still used the AC for the headlight. The voltage regulator is just a 14.3v voltage limiter (shunt). This all adds weight and complexity to what was originally a very simple bike. No plans to do this to the TY175, although it sounds like a voltage regulator might be in order?
Guy53, do you have to order parts out of country?