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I will be happy to share any information I have about the conversion, if someone want to do it. I can certainly post the parts list as well. Probably the most challenging aspect of this conversion was getting the fueling dialed in. Thankfully Todd was able to get me squared away on that. The other hurdle is parts availability. I know that Todd is getting parts lined up so that he can offer the four valve conversion as a kit.Mike, nice conversion. Will you be releasing your build notes, for example, parts used, things to watch out for, assembly sequence. Thanks.
Working on it. The 4V 820cc pistons are in; https://www.guzzitech.com/store/product/gt-big-bore-4v-pistons/A 4 valve kit? Please keep us posted.
Working on it. The 4V 820cc pistons are in; https://www.guzzitech.com/store/product/gt-big-bore-4v-pistons/
I put on my 4 valve heads and ran the bike just fine with a PC V and auto tune. Todd has been helping me dial it in, the fueling is as close to perfect as I have ever had it. I did have him flash my ECU when I was still running the two valve heads.Would a V7 equipped with PC-V and Autotune be able to accommodate the change in breathing without a remap on the ECU?
Also, the description in Todd's link to GT V7 Big Bore 4V Pistons says "... 09+ V7C-S" and doesn't specifically mention the "R". I imagine this conversion would work for the Racer as well, right?
Hey Joe, do you remember how much heavier than stock your 820 Pistons were? Did you weigh them?I put in a 820 kit from R.A.M. of Italy, and yes, I had to change the fueling. Ended up using a programable ECU by MyECU of Australia.
Good to know! Thanks for that.Mwrenn,
Guzzi Stock 750cc piston + wrist pin = 306 + 100 = 406 gm
Big Bore 820cc piston + wrist pin = 356 + 74 = 430 gm
lightened Big Bore 820 piston + wrist pin = 419 gm approx. 3% difference = heavier
I had the big bore pistons lightened by a local retired machinist. The big bore engine seems to have slightly more vibrations, but the effect may be entirely psychological because I am aware the're 3 percent heavier. I checked the big bore engine against other 750 bikes at rallies, and in truth it is in the middle range of smoothness. Some bikes are smoother, and some bikes are rougher.
Yes, it is interesting, the Pistons are pretty much as light as they can be. The wrist pin on the other hand has a lot thicker wall than the the stock Guzzi pin. It would be pretty easy to ream out the wrist pin until it's 13 grams lighter. It wouldn't take much to get there...Since your stock and big bore pistons are so close in weight, with a little machining you could probably have them end up equal.
I found a couple of different theories about the weight difference. One was that the weight difference would make the engine vibrate more. Another theory said the weight difference would merely push the point of maximum vibration either further up or further down the RPM range.
As you suggested, the 3% weight difference didn't seem to matter either way.
Todd is getting pretty close to having complete kits available. It was well worth the change for me. Really made my bike come alive.Been reading with great interest, I'm looking forward to hear more from your experience. Thanks for sharing the know how.
I have a V7 café that I have worked on over the years but keept original when it comes to the engine.
As I happened to get my hands on a pair of 4V heads I'm really tempted to go for a 820 4V conversion if this can be offered as a complete solution.
Thanks Mike. Folks, know that Mike is doing all of the real world R&D on this. Plan is to be sure when I finally offer it, we have a solid kit that will provide years of enjoyment. We're almost there. Pricing will not be cheap, as we're dealing with many un-obtanium/custom parts. Target is 55-60 rwhp. When my '16 Racer arrives next month, the fun will begin and documented here.Todd is getting pretty close to having complete kits available.