Converting Marelli EFI to TMAX : V-Twin Forum: Harley Davidson Forums

Ron Williams · 09-19-2009, 03:47 PM

I have a 99 RK with MM EFI. I am not having any problems with the MM and my build is completed. Converted to SE 95 with 257 cams, SE hi comp pistons and SE MCR heads. I am contemplating switching to the TMAX Marelli conversion with 50mm TB. I have also thought about switching to the HPI 48mm TB and staying with the MM system. I have already bought the SERT and installed a map. I have not dynoed yet and don't have any idea what kind of numbers I have at this point. I just put new pistons in because of a screw up that I made on the original set so I only have about 500 miles on the new ones. Basically I want some more breakin time before I put it through the dyno. My question is is how much can I gain by going to the TMAX conversion? Also how much could I gain by going with the HPI TB with the 62PSI regulator and delphi injectors? Either way it's a big investment and I want to be somewhat sure that the potential gains are worth the $.

barrybasinger · 09-19-2009, 08:37 PM

What you should do depends upon what your engine is capable of, and whether that TB is really the limiting factor or not. 38mm Marelli can support up to about 80-85HP. 42mm Marelli can support up to about 100HP. If your engine is not capable of 95-100 horses even with an aftermarket TB, you're wasting your money with the aftermarket TB. Remember that adding parts does not create power, it can only remove a limitation to making power. No limitation, no increase. Same for the bigger regulator, HPI TB, et al.

42mm Marelli can be had for about $300 or so. Maybe cheaper on e-bay or whatever.

Masonman · 09-23-2009, 04:55 PM

If you can hold off for a bit I might have a HPI 42MM for sale..I put it on my 99 RK about a 2 months ago, it runs good but im dropping the front cylinder and cant find out why. May be the PC or could be a broke wire somewhere. Im about spent with it and have a 42 Mikuni and stand alone Ign. that I may switch to and be done with it.. It I do that I will make you a deal on my HPI MMFX.. Thanks

Kevin
masonman10atyahoo

Ron Williams · 09-24-2009, 11:36 PM

Sounds good. I was ready to jump into the Zippers conversion a few days ago but I'm holding on and still thinking. My Marelli hasn't given me any problems other than erratic idle which doesn't bother me. Let me know when you make your decision on ther HPI. I also spent money on the SERT already so sticking with that wouldn't bother me. I'll check this post to see what you decide and we can talk about your price on the HPI. I see your from the Dallas area. I'm working on being reassigned to Seagoville. Hopefully I'll be off this rock next spring.

Masonman · 09-25-2009, 02:48 AM

Ok.. Im waiting for a test PC to be sent to me and I'll throw it on and see if that solves all my troubles.. I would really like to keep the EFI set up because im in deep with it. But I would rather ride a carb bike than sit and look at an EFI one thats running like poo!! ha

Masonman · 10-11-2009, 02:36 AM

Ok.. that didnt work, Ive got an HPI 48 for sale...It was on a couple of months and Im mounting a Mikuni on it..

Rey · 10-14-2009, 09:09 AM

Quote:

Originally Posted by Masonman

Ok.. that didnt work, Ive got an HPI 48 for sale...It was on a couple of months and Im mounting a Mikuni on it..

How much for the HPI?

Masonman · 10-15-2009, 10:15 AM

Im thinking about 975.00 shipped in the US.. I think they are about 1295.00 new..