YMS V8The next exhaust tested is another new one to the project, the YMS V8. It's easy to find for a pretty low cost and seems reasonably popular, so I thought it would make a good addition to Project 90.
It appears to be similar to the Phongeer exhaust that I am fond of, so I thought it would also be interesting to see how they stack up against each other. The YMS starts off with a nice taper made up of many pieces, where the PG exhaust uses only a 3 piece pipe to taper into the can, which I thought might give it an advantage.
Here's what the YMS V8 should look like when installed.
Unfortunately, mine doesn't look like that installed. The picture above is without the header bolter up, just to show how it should look. This pipe has been a pain.
When I started trying to install the V8 exhaust I encountered a few problems. First off, I'm not exactly sure what's up with the flange, but the only way I could get it to seal well was to use the thick gasket supplied with the exhaust and coat it with a bit of ultra copper RTV.
Once sealed, it sat in this position.
Just to be clear, the shroud was not keeping this from bolting up, that's where it had to sit for the header flange to line up well enough to seal.
Even if you don't think sticking way out and pressing on the fan shroud is a big deal, it won't bolt up. The pics below show how the bolts want to line up. The top bolt is so far forward that I would need to cut part of the shroud away in order to get a bracket to fit (shroud is unbolted and pushed forward a bit in the pic). The bottom bolt isn't too great either.
If you're thinking, no problem... just cut that bracket off and make another from scratch, there's more. It also ran into the center stand with the scooter up on the stand. I had to put the scooter on jack stands to prop it up for installation so I could make it line up right to finally seal. The stand can be used, but it's definitely not an ideal fit.
I've heard of enough other people using this pipe that I'm thinking I must have got one with something off about it. Either that or there are a lot of scoots out there with poor fitting pipes. Regardless of what the deal is, I decided to make the YMS V8 fit as it should so it could be tested.
My goal was to modify the pipe to bolt up easily and clear the centerstand without affecting the way it performs. I started out by cutting the pipe a few inches from the flange.
Then I bolted the flange and small length of pipe to the cylinder.
I tinkered with turning the pipe different ways and ended up turning the pipe ever so slightly and grinding one side so it would connect at just a slightly different angle than before. I don't believe I removed more than 2-3mm total from the length of the pipe, which should have little to no effect on performance. Once I got it turned and angled how I needed it, I propped it up and tack welded it together.
Here you can see that there isn't a lot of clearance, but it's enough.
Once it was tacked into place, I took it to the bench and finished welding it back together.
The mounting bracket was much closer to working then, but not close enough.
I chose to cut down the original bracket and only leave a small portion of it in place. I drilled a hole in what was left of the bracket and used it to attach the YMS V8 to a bracket that used to belong to one of 190mech's Peace Pipes.
Once it was complete, I gave it a coat of flat black to keep it from rusting where it had been ground and welded.
I used a 92 main jet, with the needle next to the leanest position, and re-adjusted the mixture screw. As with the Phongeer exhaust, I get a little bit of a rich sputter very briefly on takeoff at times. The only change in the CVT from the baseline of Phase 2 are 2,000RPM clutch springs.
I headed out to take a test run with the new exhaust. Roughly 5 miles into that trip the scooter started getting louder and louder. Eventually it sounded nearly as loud as if it had no exhaust. When I investigated the cause, I found that the little bit of the stock bracket that I left behind had came off of the pipe and left a large hole.
I patched up the hole with some scrap metal and welded part of the old bracket on and drilled it to work with the mounting hardware.
Finally, I went for a 46 mile ride. I got 44.76MPG, cruising around 40 most of the time. WOT cruising speeds ranged from 49 to 53MPH on flat road, sticking around 50-52 most of the time. Max speed was 57MPH. This is the first time I've lost speed versus the baseline in either phase of Project 90 to date. 57MPH happened around 8,700RPM. It felt like anything above 8,500RPM was pretty flat. Even though the max speed dropped by 1MPH, don't think this pipe offered no benefit. Acceleration definitely improved. The YMS V8 seemed more comfortable from 7,500 - 8,000RPM than any other pipe I've tested. It seemed to me that peak power would be somewhere between 8,000 - 8,400RPM. I have a feeling this pipe would have shown better results in Phase 1 with the stock porting, unfortunately I didn't own it at that point.
After maxing out at 57MPH, I came home and swapped up to 6.5g sliders, from 6.0g. I thought perhaps the V8's ability to pull at lower RPM and lack of power above 8,500RPM would suit the heavier sliders a bit better. It was a bit more sluggish getting the RPMs up to the powerband, but I was impressed with how well it operated at a little lower RPM otherwise. There was no improvement in in cruising or top speed though.
I looked over the CVT while swapping weights to see if anything seemed wrong. I checked the spark plug. I even did a compression test. I didn't see anything wrong anywhere, so I have to assume this exhaust just can't create a lot of speed because even the stock exhaust seemed more willing to rev. It could turn out to be a function of the smaller carburetor, but I think it is the pipe.
All in all, I have not enjoyed testing this pipe. Elongating a bolt hole or using some spacers is reasonable to me when installing a new exhaust. Cutting it apart and re-positioning it is not. Even without interference with the centerstand, the flange is a bit harder to seal than the other pipes I've tested. It's not a big issue, but I found it needed a gasket and RTV for a good seal every time. I have to assume that I just got a bad one since others have used the YMS V8 and I have not heard these complaints, but I don't know for sure.
I think this might be a good choice for a setup with porting closer to stock, but I have a hard time recommending this exhaust for any purpose after my experience with it. You'll just have to decide if you want to try it. I picked mine up from Taiwan. That and the amount of time it sat waiting to be tested are the reasons I didn't return it. I would suggest finding a seller in your country and trying it quickly after it arrives if you wish to use this exhaust, just in case.
