PPMPR: Project Poor Man’s Pro Race

[toratora]

So far the consensus has been that it is most likely a ring issue. ScottyDog suggested getting a BRK ring. Which I might do in the future—when I have the luxury of time.

For now however I’ve followed Remi’s lead, and ordered the Metrakit ProRace 3 kit. Which hopefully will get here soon enough for me to put it all together for the Nineteen Nineteen ride.

I’ve run the older version of this kit previously, and I liked it. I expect this one should be quite serviceable as well.

[toratora]

Oh yeah sorry. I forgot that you have to remove the plastics and remove the engine. I can just remove the cylinder in 5mins, with almost no fairings

It sound me a ring issue, my buddies had about the same simptoms as your bike. Never give up, I would be really interested in how does the 77 and 88 compare to each other on a video. You will have to do one decent video for us keep it up

It’s highly unlikely that I will ever make a video for the Stage6 kits. My bikes need to be reliable, and so far the Big Racing kits have proven theirselves to be unreliable. Therefore they are likely to all be decommissioned—including the BR88.


Of interesting note back in January I was getting the same low compression with this kit, and there was already some slight scoring.

[jkv357]

Of interesting note back in January I was getting the same low compression with this kit, and there was already some slight scoring.

Do you think the low compression is causing the current problem then? Did it run OK back in January with the same low compression?

Seems like something else is going on.

I'm not sure, but can low compression itself cause the excessively rich mixture you look to be getting?

[Rj_666]

This news is SUPER disappointing, as I was considering these BigRacing kits for my Aprilias. Although even more disappointing for Tora, I'm sure.

[toratora]

Do you think the low compression is causing the current problem then? Did it run OK back in January with the same low compression?

Seems like something else is going on.

I'm not sure, but can low compression itself cause the excessively rich mixture you look to be getting?

Well I’m befuddled. Up till Sunday the bike had been quite ridable after I did two things. Put a 15 tooth sprocket on the front, and started running the stock ignition. It still sucks at starting from a dead stop, and that got worse at that over time, because it had such a hard time revving up. When it was struggling to rev up it made a lot of smoke.

Clearly the compression, which shows the same as back in January, isn’t the problem. I’m intentionally running the carb a little rich, but the bike actually runs better with the choke on than with it off, so that would indicate that it’s not rich enough, but there’s no wash, which indicates that it’s too rich. But now the bike wont run at all—just like the Silver bike.

I am going to try cleaning out the carb before I pull the top end, but right now I really don’t trust these kits.

This news is SUPER disappointing, as I was considering these BigRacing kits for my Aprilias. Although even more disappointing for Tora, I'm sure.

Yeah I don’t know what to say. For now I’m going to install a different kit on the bike. Considering that I have three Stage6 BR kits I am very disappointed.

[jkv357]

I am going to try cleaning out the carb before I pull the top end, but right now I really don’t trust these kits.

Do you have a "known-good" carb you could swap to see how it acts?

Not sure what would cause the odd mixture issues, but it sounds like something isn't right in the carb.

Are you running the oil injection or pre-mix?

[toratora]

On this engine (well any BBK really) I run premix at 32:1.

I really don’t believe it is the carb, but it is easy enough to pull it, inspect it, clean it, adjust it, refit it, and give it a test, so I’ll try it.

I could pull a carb from another bike, but again I don’t think it’s the carb, and if it is the carb I should be able to notice an issue when I tear down the one on the bike. Still it’s an option, and if I find myself twiddling my thumbs before the other kit arrives I’ll probably try it.

[kaldis12]

You saw it smoking a lot? Now thats the same issue what I had with my setup. Cylinder head O ring blow up, causing it to be lean and rich at the same time. It can decrease compression at the same time. A head O ring change could be worth the time. It explains why you wasnt been able to tune it and why it has a low compression and of course the smoke.

[toratora]

It could be the head, but why would it run fine on previous rides, and most of the day on this ride? I’ll be pulling the top end off of it soon, so I’ll be giving it a good inspection then. It would be interesting if that was the problem. However, on both of these engines I did run a leak down test before running them.

[kaldis12]

Could be that the head is not perfeclty flat. It could be a bit off and when it heats up it leaves a gap if you know what I mean. Im really sure its going to be a leak issue. I had the same issue. Sometimes its pretty hard to notice, I was like. Mine was really noticable. Truing the head and new O rings could solve the problem IMO. I hope