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2012 V7 with 4V Heads
- Thread startermwrenn
- Start date
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.
He is also going to offer the four valve kit with an 820cc option as well.
So he has it covered if anyone is wanting to convert their bike.
sign216
High Miler
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/
That is really cool Todd, thanks for continuing to give us the most options for our beloved V7s!
francod123
Cruisin' Guzzisti
Todd, for those of us who have already remapped our ECU with you, will we need a new remapping if we got this big bore kit?
pokeyjoe
High Miler
Since Todd's not jumping in (he's either working or enjoying the day), I'll field this one. The answer is yes. You're increasing the displacement of the engine. More air will move through it and you will need more fuel. And that's just going to 820cc. If you add the 4 valve heads, you will move even more air and need more fuel.
sign216
High Miler
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.
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?
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?
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.
The conversion will work on the Racer as well. Todd is going to convert a new Racer as soon as they arrive in the States.
Hey Joe, do you remember how much heavier than stock your 820 Pistons were? Did you weigh them?
sign216
High Miler
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.
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.
Good to know! Thanks for that.
My stock Guzzi 750 2 valve piston/wrist pin/rings weighs 411 grams
The 820 flattop 4 valve pistons/wrist pin rings are 424 grams.
So they are really close. Interesting that it is the same 13 gram difference that your kit had.
I don't think the difference is significant.
Thanks for sharing your info and experience with a big bore conversion.
Cheers
sign216
High Miler
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.
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.
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...
Cheers
An interesting day today, there is a new shop in town with a Dyno, so I took my V7 4V over and ran it.The bike makes 26% more power than stock. 49.67 HP at the rear wheel. 43.2 ft/lbs of torque.
I can certainly tell the difference when I ride it! The plan now is to install Todd's big bore kit, do some porting, bigger valves, hopefully a cam. I believe a realistic goal would be 60 HP. Going to take some more work to get there.
Actually, the bike hauls ass like it is, pretty light and nimble too. But more horsepower is always good!
Many thanks to Todd getting me to this point, it would have been impossible without all his work on the fueling. When he gets his 4V Racer done, it is going to be a RACER!
sign216
High Miler
Your engine looks like a real performer. A big bore kit and bigger valves will be fun modifications.
Keep us informed.
Keep us informed.
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.
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.
Todd is getting pretty close to having complete kits available. It was well worth the change for me. Really made my bike come alive.
Thanks for your interest!
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.