Piaggio hyper race on rexy frame, the true sexy rexy.

[Lucass2T]

Congratulations with finding the problem. And congratulations with the Yasuni R.
Change the carb to a 19-21mm when you put the Yasuni R on. It wil run better with better pick up, easier tuning and wayyy less fuel consumption.

Remember you are running a machine thats like Usain Bolt exhaling through a straw. With the Yasuni R it will get better but that 28mm carb is way overkill. Change to a 19 or 21mm and it will rip!!!

[808ministroke]

Nov 10, 2020 8:24:47 GMT -5 Lucass2T said:

Congratulations with finding the problem. And congratulations with the Yasuni R.
Change the carb to a 19-21mm when you put the Yasuni R on. It wil run better with better pick up, easier tuning and wayyy less fuel consumption.

Remember you are running a machine thats like Usain Bolt exhaling through a straw. With the Yasuni R it will get better but that 28mm carb is way overkill. Change to a 19 or 21mm and it will rip!!! 
I was told by the person who built this engineThat a 24 mm card is the smallest he would Dare to go. I've used various calculators in such to determine the optimal venturi size and they all point towards a 28 that's also what's recommended for this kit acording to malossi,  And I believe that the increase fuel consumption is well worth the increased cooling potential and even increased top and potential although it may be very slight. I  Had a 24 mm round slide but it is leaking fuel otherwise I was going to attempt in using that carb If I get jets for my 19 mm big enough then I guess I can attempt and just see how it runs but for now I am using the 28 also it better matches the exhaust port size and I'm pretty sure you want the same intake as well as exhaust diameters

[aeroxbud]

This is an interesting graph Brent made using horsepower and carb size recommended by Mikuni and Dellorto 49ccscoot.proboards.com/thread/1366

[808ministroke]

You know i can only guess how many horse power were in any of my builds.
I think a piped polini corsa with bigger carb and tuning can put out like 10-15 hp?
If the above statement were true i could only assume my kit makes a bare minimum of 15 hp and with the optimal set up can probaly pull like 20-22 hp im thinking, peak rpm is also relevant in venturi size

[808ministroke]

 Hey guys this water is not from an outside source it didn't rain there is water comjn out my exhaust  i can only awesome a base gasket i.e. a fuckin rebuild danm wtf
.

[Lucass2T]

Use a light coat of silicone sealant when re-assembling. Also on the head gasket.

[808ministroke]

Nov 13, 2020 7:31:39 GMT -5 Lucass2T said:

Use a light coat of silicone sealant when re-assembling. Also on the head gasket.

I will for sure, i did not assemble this engine but have assembled the mina mhr before, i am assuming itdba basebgasket and not a head is because of how these bores seal making a head gasket failure highly unlikely.
I havent yet looked at it any deeper but based on the fact these piaggio engines have water flowing into the bottom of the case it seems more likely that the failure ocurred there, i can only pray that it is not a leak inside the case itself at that point it may be beyond my pay grade tp fix.

[aeroxbud]

I know Piaggio don't fit base gaskets to their hyper 2 engines from the factory. But if someone else built it, you will have to investigate.

[808ministroke]

so i took off the old exhaust and it was filled with was filled with water maybe like a half cup or so i ran thr pump with the exhaust off and and i did see a few drop seemingly come out the exhaust from the side closest to the head.
so that leads me to suspect it is a head gasket failure of some sort. I always liked the modular head design that is on these and a few other top end bores, always thought they were impermeable to failing but this weekend i am gunna take a look and i actualy do have on hand a replacement head gasket for the mina 77version which i think is identical to the head gaskets on all the 50mm mhr bores so crosssing my fingers.
if that is the reason water is leaking into cylinder i will consider myself really lucky as that is the one thing i can quickly and easily replace.
oh and got in my yasuni r , nice silencer and bracket i wish the chamber was a little bigger though, still if i can fix the engine up and even get to run it at all this weekend i will be super stoked.

[Lucass2T]

Make sure to remove the restrictor from the silencer

[808ministroke]

the restrictors in silencers come removed if you order from st.ca .
So I took off the cover over the head and upon it expecting the Cylinder studs it was apparent to things were not quite right.
The 1st and most notable thing was the amount of rust around the nuts that held the head to the cylinder I'll show you a picture on the bottom of what I mean.
Next the bottom right stud if you were looking at the cylinder from the spark plug side was loose after attempting to loosen in retie in I realized that it was in fact the stud itself that seemed to have come loose I was able to tie in the stud back in using the nut however after that I tried to tighten all the nuts backup and it seems that either the nut itself or the stud has damage threads from looking at it it looks like you could go either way but I'm leaning towards it being the nutShould be piece of cake to replace that right?
Wrong these piggy nuts in studs are narrower than mina ones.
I have been important question for everybody and that is I should have to replace all of these nuts and maybe even the studs as at least the nuts were not the proper material for a water cooled engine with the modular head meaning these nuts are gonna be constantly submerged in water I never had a problem with my other mhr getting rust in this area I can only assume that the wrong nuts were used hopefully the studs are the right ones I don't even know where to get these studs knew if I needed to I'm on a try to go to home depot today and see if I can find him a placement set of nuts and hope to God that I can get them to tighten on to the studs this was obviously my issue as where the water was leaking into cylinder was the exact place where the stud was loose. Any and all expertise would be greatly appreciated.

[aeroxbud]

They look like some nuts someone has picked up from the local hardware store.
Piaggio has dealers in the U.S. So shouldn't be too hard to get the right nuts and studs.

[808ministroke]

yah its weird that these nuts would have been used by somone with enough knowledge and skill to properly machine the case to fit the bigger bore and stroke. after looking a little deeper seems as though the bottom stud on the variator side needs to be replaced and probably want to replace all studs and nuts .
problem is i cant find the right studs anywere they are m6 not m7 like minarelli not entirely sure of legnth but 106 is stock legnth and having a stroker crank these should be a little longer anyone who can help lead me to a source for these will be my hero.

[190mech]

Steel will not rust if the proper amount of antifreeze is used..Honda 2strokes use 6mm studs and their stroker kits have longer studs,perhaps you could cross it over to those..The threads may be stripped in the lower hole of the case,might need a helicoil there..

[808ministroke]

wow after looking on web especially treatland there are alot of diff. studs. i did not know this but aparrently some vespa studs have m6 on one side and m7 on other.... i am assuming that these and modern piaggio hyper2 engines use m6 on both sides , right? tomorrow i will take the entire head off and remove the bottom left stud all tue way to measure it .
and 190 guilty as charged i have been constantly changing my coolant lines around even had a hose come loose and lost all fluid a few times so i was just running straight water i know thats not ideal but i did not know the effects would be this devastating.