PPMPR: Project Poor Man’s Pro Race

[toratora]

My neighbor asked me to use a bike to save his parking spot. I did so, and gave him the keys since I would be gone for the day.

When he got back he moved the bike, and put the lock on it, but left the ignition key not only in the bike, but on killing the brand new battery! I pulled the battery out, and it seems to have charged up. Back in the bike now. Hopefully it will be fine.

[jkv357]

My neighbor asked me to use a bike to save his parking spot. I did so, and gave him the keys since I would be gone for the day.

When he got back he moved the bike, and put the lock on it, but left the ignition key not only in the bike, but on killing the brand new battery! I pulled the battery out, and it seems to have charged up. Back in the bike now. Hopefully it will be fine.

That's like "strike 4" - left the key in it - really?

Lucky it was still there when you got back.

No good deed...

[toratora]

Sometimes it feels that way, but everyone gets stressed past their limits, so it's hard to say. Thankfully nothing bad happened, and everything is back to how it was before.

[toratora]

I was chatting with ScottyDog about how with this bike the power doesn't really show up until around 10.5K, and well here's why.

The top graph is the ignition curve with the Top Red box that I have installed on the bike. The lower graph is the power curve of the BR77 kit on the bike. When you combine the two it becomes quite obvious why this bike has no power below 10.5K RPM!

Now there are a couple of options. I could pull the flywheel and rotate it making the curve come in sooner, but that would probably make the bike very hard to start, because the lower part of the curve would effectively disappear.

The second option would be to go back to the stock CDI. Since the kit was tested with the stock CDI this is probably at the very least worth trying.

Sure it wont look as sexy as the Red box, but the bike would probably be a whole lot easier to ride, and still produce plenty of power.

Scotty also told me that these kits were designed to run with the stock ignitions. He discovered this while talking with the designer of the kit.

[toratora]

I finally had a chance to do some minor work on the PMPR. There’s still a bunch of things I’d like to get to on the bike, but it sure is nice to have gotten through some of them.

The plan for this bike is to return to the stock CDI unit to compare it with how the Red Box has been performing. The Red Box is so aggressive, and combined with a cylinder that is already aggressive made for a bike that wasn’t a lot of fun in the city, and quite a challenge (although fun) in the hills.

At the start it seemed prudent to take a bunch of wash photos with which to compare in the future. Things appear to be fairly rich. There doesn’t seem to be any carbon building up anywhere. The dark areas are just the lack of light reflection from the ports. Also, there is some slight vertical scoring on the cylinder. I should have also tossed the compression gauge on it to get a baseline reading with which to compare the Silver bike.




The CDI swap went well. I did noticed that the paint on the frame wore thin where the Red Box was mounted. I’ll have to address that soon. The bike started right up, but I have yet to take it for a test ride to see how it compares. Had more little things to attend. I had a very clean CDI unit to install, but it doesn’t look nearly as nice as the Red box looked in there. It’s quite probably that I’ll have to adjust the jetting now that the stock CDI is installed.






When the wind blew the bike over a number of things were damaged. One of those was the right side front blinker. Thankfully the lens survived and I was able to use some old blinker parts to make it all fresh again.


The last little treat for this bike was a red pillion seat. Paul gave me a parts stash, and in there was the red pillion. The material is wearing thin in a few spots, but the over all look really fits the bike. A few more things on this bike need attending. I need to fashion a new master cylinder reservoir mount, flush the brake fluid, and it would be nice to get the other pipe back, and installed on this bike. Boot burning isn’t one of my favored activities. I could modify this one, but it’s best to save this pipe for the RS which will eventually get its turn in the cue. I also want to dig out one of the rear huggers for this bike. The open rear tire does look cool, but the hugger helps keep it cleaner.

[toratora]

https://youtu.be/IsvfofcIE1Q
I really needed to get the front brake master res dolled up on this bike. I remember that there was a res that came with the stuff from Paul, and decided to try to install it on this bike. It really didn’t want to work though. I had to do a lot of messing around getting it to work with the Brembo 16, but eventually it worked out. The res is a bit yellow, but seemed serviceable.

Another issue was clearance. Because it is larger, and the GPR wasn’t designed for this configuration the available space is quite limited. Also the hose came from a larger nipple than what the Brembo feature. I’m going to have to find some tigon hose to install on it.




With all this done it was time for a test ride. The bike is running much better with the stock ignition CID over the Red Box. The difference is quite noticeable. The bike is much more ridable, but no noticeable lack of power compared to what it was like with the Red box. It would be nice if the power came in just a little bit easier. That might be possible to coax out of it with an ignition that could be programmed.

The red pillion really looks nice on this bike. It’s also a whole lot of fun to ride this bike. It spools up very nicely, and pulls really strong. And it handles like a dream. The brakes are a little wooden. It would probably be nicer to get a smaller master, or upgrade the caliper to one with four pistons.

Now that the bike is running better I noticed that the carb needs some servicing. I think it might have an air leak on mixture screw. It takes a long time for the idle to come down after blipping the throttle. Which would ordinarily indicate an air leak. Since I checked the block for air leaks it could be coming from the carb, rear manifold, or something like it.

[toratora]

Working hard and making no headway. I’m sure all of you can relate to that feeling. Today was employed attempting to suss out some issues with the PMPR. The idle is getting hung up, and doesn’t come down for much longer than it should. I hypothesized that it might be an air leak at the mixture screw.

It turns out that the MetraKit version of the PWK doesn’t employ an o-ring at the mixture screw. The OKO that I have (but have not used) does, so I took the mixture screw from it, and tested it out on the bike with the MetraKit carb.

The results were surprisingly the same. I could get it to behave slightly better with the screw turned all the way in. This tells me that the pilot jet could be suspect. But there were other indicators that suggest that the main jet is too rich, and I will attend to that first.


The plug still indicates that the bike is running rich, as does the wash, but it looks less rich than it was with the Red box. Which is an improvement to be sure, and correlates with the performance of the bike. It appears that I will have to re-jet the carb to adjust for the richness, however it is running quite well with the exception of the hanging idle.




To compare with the Silver bike I got out the compression tester. I don’t really put a lot of faith in the car testers with these little engines, but they should deliver repeatable results. The first reading I got with the gauge was right around 100psi which is what I saw on the Silver bike.

Repeated tests would only produce slightly more than 75psi. I believe the reason for this disparity was my inability to properly seat the gauge to the connector. It seemed to be binding due to a conflict with the coolant hose.

I also noticed some similar scoring on the cylinder wall much like on the Silver bike. Still this bike runs, and the Silver bike currently doesn’t. I will have to continue the investigation.


Another issue that popped up was in the battery department. Like in the DRP the battery in the PMPR isn’t holding a charge. I couldn’t even get it to take a charge from the Ballistic Intelligent Charger. For the time being I installed the Yuasa from the Silver bike.

[jkv357]

The results were surprisingly the same. I could get it to behave slightly better with the screw turned all the way in. This tells me that the pilot jet could be suspect. But there were other indicators that suggest that the main jet is too rich, and I will attend to that first.

Have you sprayed anything around the intake boot and reed block connections to check for a leak there? Seems like there is a vacuum leak somewhere.

The idle mixture screw is an air-bleed - right? If so, bottoming it out will make it richer and would also suggest a vacuum leak to me, especially with the hanging idle.

[toratora]

Various carbs work differently with regards to the air mixture screw. My understanding with the PWK type is that all the way in is the most lean, and as the screw is turned out the mixture becomes richer. At least that’s what I’ve gotten from the docs.

When I built up the engine I did employ a leak test. This doesn’t check the connection of the carb to the intake manifold, nor the connection to the air box. It also doesn’t test for exhaust leaks. The reason being is the test runs from the intake manifold to the exhaust manifold. On this engine that path passed the test.

Also, this carb exhibited this behavior on another setup, and is thus suspect. I think I purchased a rebuild kit for it, and the kit didn’t actually fit, but that was long enough ago that I don’t know for sure.

I agree that it is acting like an air leak, but it’s also possible that the pilot (slow) jet is just too big for this setup. I have some PWK pilot jets (somewhere!), but since the main jet is still off so I should probably focus on that first. However, if I locate the pilots I will probably try going one size down—even though it’s generally not a good idea to change two variables at the same time.

Currently the main jet is a 106. The BR88 with the HPI (which makes comparisons difficult) is running a 98 (but not tested). I’m not sure what’s in the Silver bike (BR77—the same kit, and now mostly the same setup except for the pipe, and carb brand), but that bike isn’t currently running—so it’s not a proper comparison just yet.

Hopefully, we’ll get some nice dry days soon, and I’ll get a chance to move forward with the carb tuning. Thankfully the bike is pretty close now, and already a lot of fun to ride. I’d also like to try a 15T on the front sprocket. The 14T is pulling nicely, but the top speed suffers, and I think this engine should be able to comfortably pull a 15T.

[jkv357]

Various carbs work differently with regards to the air mixture screw. My understanding with the PWK type is that all the way in is the most lean, and as the screw is turned out the mixture becomes richer. At least that’s what I’ve gotten from the docs.

I agree that it is acting like an air leak, but it’s also possible that the pilot (slow) jet is just too big for this setup. I have some PWK pilot jets (somewhere!), but since the main jet is still off so I should probably focus on that first. However, if I locate the pilots I will probably try going one size down—even though it’s generally not a good idea to change two variables at the same time.

All of the carbs I've worked with that have an idle mixture adjustment in that position (behind the slide) are air-bleeds. That would agree with my theory about the vacuum leak (hanging idle, best with screw all the way in).

As far as the Main Jet size, how was it running out on the road at WOT?