Saturday, May 5, 2012

Update on DR70 upgrade

Well, a few things have transpired which I can report on.
1) First off: after finishing my first tank of gas, I averaged about 49mpg. I am very happy with this, actually, because it is better than I had been getting with just the SP3 pipe on the stock engine.

2) The 74 main jet is too lean for the kit plus the SP3 pipe. Although my mixture was quite good through the midrange, I discovered that going to a larger main jet was what made the full throttle bog go away. So, if you have a Sito+ or SP3 pipe, and it is derestricted, use something bigger than a 74 main. The next sizes I had were an 82 and 84, so I couldn't try any intermediate jets. The power felt a wee bit "soft" with the 82 and 84 so I think an 80 might serve better. But really, I'd start at an 84 on a given bike and work backwards carefully.

3) top speed: with the 82 and 84 main my top speed was about 47-48mph indicated. This was reliably reached on a flat, and I'm pretty happy with this, particularly since my primary goal was improved power during riding and not top speed per se.

4) I soft-seized. I am VERY disappointed about this - "broke" my brand new top end. I do not believe the soft-seize was due to mixture being too lean - the plug color was very good and I was running the 82 main jet at the time. Also, I was doing this after a 100 mile break-in period (as opposed to the 200+ mile period suggested by the manufacturer. Possibly bad chamfering, high heat, and an insufficient break-in period.
Let my tale be a warning.

Next step is to find someone with a ball hone, and get my hands on some fresh rings I guess.

*Edit* I am convinced the soft-seize was because I did not have enough oilllll. Trickiest part here is adjusting the autolube correctly. No more issues after cranking the auto-oiler up a bit more.