Fun on Rockhopper

[Humsuckler]

ah nice lol
im a yammy boy forever. i knew that was some 80's ish yz pipe haha

 

[Dave31]

Trying out a new muffler, gonna take her for a spin here and see what it does. If it's the same or better gonna clean it up and make it look somewhat descent.

 

[Dave31]

Lost a little top end with it, still got plenty of low end. Crapping out on me but friends showed up so I did not have time to mess with the carb. I like the bigger pipe better.

 

[Dave31]

Here is a short video of Alex on the R Hopper with the 1975 Yamaha GTMXB 80 pipe so you can hear how it sounds.

RockHopper Video :: Alex on Hopper video by FR31MB - Photobucket

 

[Dave31]

Finally mounted the bigger carb, no more four-stroking or crapping out like I like to call it. Hopefully tomorrow I can make a video to show the difference from the stock carb vs the bigger carb. I still need to get a air filter as well...........

Motor runs smother and less vibrations, I am curious what it will do with the bigger pipe. I am torn between the pipes. I like the performance of the bigger pipe but like the way the smaller pipe fits and looks.

 

[Humsuckler]

ah id stick with the older pipe with the heat sheild, even if you have a little less top end.

i was thinking tho, you can probley try putting a stinger tube on its outlet hole and you *might* get some of the top end back

 

[Dave31]

ah id stick with the older pipe with the heat sheild, even if you have a little less top end.

i was thinking tho, you can probley try putting a stinger tube on its outlet hole and you *might* get some of the top end back

Thanks for the advice Humslucker, I am gonna give that a try.

I plan to add a reed valve as well, as soon as I have the time. Probably won't be for a while though.

If I can get off work early enough today I will make a video of the two carbs. My stock carb starting crapping out real bad, no matter what I did I could not get enough fuel into the cylinder.

The bigger carb solved that problem, it still will crap out for a second or two but not all the time like the stock carb.

This thing is starting to run so good I am not sure I want my friend racing it the DR.... He might beat me lol.

 

[Dave31]

Last night when I installed the carb it ran good, needed a little fine tuning but ran good around the hood.

This morning I was horrified when I was leaving for work and it would not run, I messed with it a little but never got it running. So I had to drive my truck to work, then found out my battery in my truck was dead from setting so long.

I have messed with the crab all night and still I cant get it too run. Acts like it is getting way too much fuel. So I put the jet from the stock carb and it still will not run. The only way I can get it too run somewhat decent is to create a vacuum leak. I find it odd it ran good last night and now the only way to get it running is with a vacuum leak.

I think I am going to get a bigger jet for the stock carb and use it. All the jets I have are too big and I do not want to drill the stock jet. I don't have any bits small enough anyways.

 

[the new ausped]

you need some piston rings man there cheap as 2-stroke smoke and guzzling feul are 2 very good signs of bad rings the ones on your bike they woulld have, what 3000kllms on them? (or are they the origional ones?) my friends 2 stroke dirt bike has the best piston rings specialy made in america and shipped to aus and they last bout 600miles,

you said it only started smoking after last octobers death race thats proll coz you caned it and it hadnt been caned for a while and those poor little rings got the crapps

 

[Dave31]

Yeah I know the rings are going bad, rings that last only 600miles? No Thank You lol. If I do change the rings I will go with Wiseco. But I have no plans to tear the motor apart again.

Been spending the morning jetting the carb. I have a bunch of jets but only a few close to the size I need. I can get it running good but not perfect, either I am a little too lean, or a little too rich. I need a jet right in the middle.

 

[yamahonkawazuki]

Just having a little fun on my Rockhopper. I forgot to adjust the helmet cam cause I sit more upright on the cranbrook. Hope you enjoy it..........

Haha WOW nice work. nice work indeed. can i get a spec on the powertrain? which kit and whatnot? or was this custom a oneoff?. again, nice worka

 

[Dave31]

It's a old King's bushing motor from 2004

This motor is approaching 10,000 miles on it. I had a crank seal blow out on me the other day and I've got new ones just need to replace them.

It's basically stock with very light porting and about 1-1 1/2* of timing advance. The intake manifold has been polished up a bit for better flow. I also run mothballs in the fuel for DR

 

[john_the_great]

It looks like you went grave-robbin' a poor Yamaha gt-80! Let the dead rest in peace!! Your reanimating old motorcycle parts like Frankenstein! jkjk its just I am currently restoring a gt-80 so i instantly recognized the pipe and carb.

 

[Dave31]

Magneto determines top speed?

Recently on my Rockhopper I had a seal blow out on the mag side. The mag got soaked with fuel and I dried it out and replaced the seal.

It worked for a few days but then on my way home from work my motor just died and I determined right away that I lost spark. After pedaling home I swapped out the mag from my Huffy cranbrook.

My cranny being a 50cc stock motor and just a commuter bike tops out at 27mph. My Rockhopper (71cc)with some engine mods tops out at 40 + something mph

Well after installing the mag from the cranny onto the Rockhopper my top speed is 27mph. I have tested both mags before and the cranny mag was a little weaker, but not by much.

I find it strange that the mag would make such a difference when they are so similar as far as output.

 

[Humsuckler]

very interesting indeed....
i dunno either! chinese special secret i guess

 

[Dave31]

After weeks of testing, trying different carbs, pipes and all combination's as possible.

Back to the stock carb and the freakishly over sized pipe works the best with low end torque and top speed.

 

[tyrslider]

Good lookin' stuff Fair! The front sus. RockHoppers and HardRocks make great platforms.

You build a mean racer!

I think I wanna do sum'm similar w/ a 4 stroke shifter.

 

[Dave31]

Just got back from a nice long warm Sunday night ride, it was really great! Love Sundays nights the streets are almost dead with traffic.

 

[Dave31]

Here is a short video of the fun I was having in a empty closed off parking lot.

RockHopper Video :: rockhopper.flv video by FR31MB - Photobucket

 

[flybytaco]

I need ring, piston & cylinder!... but we will try to squeeze one more race out of my china girl and hopefully get her mounted back on my Della Cruz. After every race this little china girl says "No more!, No More!"

i have whatever you need just pay the shipping and i'll hook you up