Yamaha Yamahopper qt50 top speed run, hang on!

Some further tweaks yet but 49.1 mph. Almost there. Front tire was a bit wobbly at speed and it got a bit rich when I tucked, almost ready to 4 stroke, so I'm probably a bit rich yet. Top temp was 392F so not sure I want to drop the main jet much at all.

Assuming max rpm is 13k on that engine and assuming use of IRC 70/90 tire and assuming 95% transmission efficiency and assuming use of stock rear gear - I calculate max speed as 51.1 mph. Assuming PW50 rear gear gives 12.5% speed boost over stock and assuming engine can turn that same as stock gear, max speed would be 57.48 mph.

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[jrosario]

Watch the barn go by ...lol love the speedo image at the end 😮

[jrosario]

The smaller the bike the faster you think you r going. Rollercoasters top out at 25mph

[dannywyand]

That is one sweet ride you have there. Purrs like a kitten!

[gpyt]

NIIIICE!! She starts hittin the sweet spot and singin opera right at about 1:17 / 40/45 mph!! I hear you though, head temp don't lie, richer means cooler...aka life support esp at the upper ranges, slight 4-stroking, but still pulls strong! Did you change your clutch springs (if so which springs) and do a rear gear / rear end pw50 gear swap?

[jrosario]

The scenery tells the story. Looks like 30 mph . 48 mph sure buddy

[garrettprosser]

So a pw50 rear gear will give a speed boost you say?

[dannywyand]

I have a 79 QT50 that reaches 32 to 33 mph stock. My 86 QT50 reaches about 30. Seriously thinking about installing a big bore kit on one of them. It's great to have access to really good info on how to do it right.

[bryanbell]

What is the set up you're running? The link in your other vid isn't working. I love your vids I have 3QTs and 1 towny none of them ran when i got them now most have 60cc kits, blew up a few and then rebuilt the top ends before I got the jetting right with about 100 main jet. Where do you get the pilot jets for these? When I soft seized I was hauling ass down hill and cut the throttle to slow down and the lack of gas (cooling) seized it. Now I kinda use the brakes while keeping some throttle going so it doesn't happen but I thought some larger pilots would help. Keep up the posts love watching them!

[rerobertson]

You got a performance pipe on there? I stand by a trail tech too! I’ve seen the temp that I’ve soft seized at and plug chopped and rejetted accordingly.

[jackrutherford-]

I think my next move is to go with a bigger rear tire. I've got an IRC NR 77 80/90 I can install. Bigger tire should give me about 1.8 mph more if I can spin it at the same rate. Speed test to follow.

[Fisch_gamer]

I see allot of people (treatland chart) calling for 70-90 main jet even with kits but see you are running over 200. Why do you think that is,

[TheJustenpm]

That is a top speed WOW. 48.3mph that is the fastest my qt has gone. It's hard to explain what is is like doing 45+ on a qt...nice job I think you could hit 50mph

[jackrutherford-]

You know you're going fast when 20mph at the very end as I'm rolling to the stop sign seems dirt slow.

[jrosario]

A bigger tire will not do anyrhing but throw the speedo calibration off even more. You should really get over these 50cc bikes ang get a honda rebel

[angelocardoc]

WOW!!!! Dare devil.

I get a solid 33 mph on my QT.

[mattsgarage]

I have a 83 express and it goes 27 but if I take the air filter off it does 32

[jrosario]

These things were designed for 25mph. If you want to go fast its easier to get a bigger bike engineered for it. You are just taxing the engine to shorten its lifespan! Genius