MarsN

I definitely was making the mistake of too rich with the main jet when I started with the Factory pro kit. This was on the original 1127 with K & N filters and Kindle 4-2-1. The Factory Pro recommendation was too rich for my environment/set-up. I think I went two jet sizes smaller than their recommendation. I was pretty diligent however in my test runs to try to find the right size main jet first. Tried over and under on main jet size. However, trying to feel subtle differences at full throttle when getting close to the right jet is definitely tricky. So I could still be too big based on the fact that I'm at the leanest needle position as well.

Searched for this specific question no luck.... Looking for some feedback/experience with jetting changes after a similar engine rebuild to mine. I am getting close to assembling my 1216 rebuild and I want to have the jetting as close as possible to 'acceptable' for the initial start-up and break-in, especially for that first half-hour of run-time. I've done some reading on the affects of increased displacement, increased head-flow, and increased compression ratio and all three indicate a decrease in richness, which I admit, was opposite to what I would have guessed. So smaller main jet and leaner needle position are likely needed. Rather than specific jet sizes, or needle position, which is going to be individual based on exact engine specifics and altitude, and other variables, etc. I'm hoping to hear some feedback on just how much of a change I should be looking for. ie 1-2-3-4 jet sizes smaller? I realize I will have to go through the usual steps of dialing in the jetting as I normally do. IE full throttle runs to find best main-jet, followed by needle-jet clip position, float height etc. But just wondering if anyone has any first hand examples of how many main jet sizes they had to change, or how many clip positions etc, with a similar engine rebuild as mine. I have BST38SS carbs nicely set up before the rebuild. I have the Factory Pro 38 mikuni jet kit installed. Think I have a 152.5 main, and needle at top(leanest), or possibly second from top clip position. I live at 1100 meter altitude which leans things out too. The following are the engine changes: -1216 JE kit -11:1 -Head ported by experienced oil cooled head porter -30/26 valves -stock cams Any experiences or feedback is much appreciated!

Old thread, I know, but I have to chime in, in case someone reads this.... I'm in the process of adding an auxillary head cooler to my '91 1216 so I've been reading and measuring... There is an important hose size distinction to realize when plumbing the head cooler lines. People are correct when they state that the cylinder head valve cover lines are AN6. however, those lines have been split into TWO AN6 lines from ONE AN8 line coming out of the crankcase(the 'Y'). Using the approximate i.d. of AN6 vs AN8 lines, the area/volume of one AN8 line is very close to the same as two AN6 lines. Eg. area of AN6 id of 8mm = 50 square mm's. area of AN8 id of 11mm = 95 square mm's. So you can see that splitting one AN8 line into two AN6 lines keeps the volume close to the same. This means in order to preserve the same volume and pressure of the oem system(probably important), the lines running to and from an auxillary cooler need to be AN8. The spit into two AN6 lines keeps the volume/pressure the same because there are TWO lines. If running AN6 lines for ALL hoses connecting an auxillary oil cooler to the head, you will be greatly reducing the oil volume being supplied. The pressure will be higher for sure, but will it be enough higher to maintain the same oil volume intended in the design? My guess would be no. Much better to stick with AN8 lines to and from the oil cooler, and only use AN6 after splitting into two lines going back into the head valve-cover. One other note. When measuring the id of the oem fittings going into the valve cover, they are ~ 9.6mm. however, the opening in the valve cover itself is only ~8mm. The diameter of the opening coming out of the crankcase(the single side of the 'Y') is ~11mm.

Ok that’s good to know. Sounds like OEM springs can handle a little more weight and lift than OEM specs. btw, the reason I was wondering about SS valves in OEM guides is that I read a couple articles that mentioned stainless steel needing bronze guides as ss can have friction issues with other metals. However, the ss valves sold for our bikes at least, have either chromed, or nitrided stems. I assume this is for friction reduction so makes the guide material less significant.

That sounds right, cant be too much extra weight with 1.5mm larger diamer valve. Oem are probably hardened steel which shouldnt be much lighter, if at all, than SS. Planning on using new oem springs, so no worries about sag/lost temper etc. Oem guides are available from places in Japan that sell new old stock. Am I allowed to state a vendor?...rhymes with "me bike". Only $5 too! hence my curiosity vs bronze. Think i'll go with bronze though(if needed at all), lots of positive testimonials. thanks for the input.

Hello boys and girls. Long time reader, first time poster. Love the site, hoping for a little experienced feedback.... Finally starting my engine rebuild during the long Canadian winter, gathering parts. Plan: 1216, 11:1, port, 30/26 valves, stock 86-88 1100 gix cams, 38CV's(with Lee's stepped jet-needle washers, thank you), Hindle 4-2-1. My questions are: - Regarding the increased weight of oversized stainless steel valves over oem, is it enough to warrant stiffer than oem valve springs? I'm thinking if I use titanium retainers this may keep the valve train weight close to oem so that oem springs are sufficient? stock cams/lift. Anyone know the difference in weight between a 30mm or 26mm ss valve vs the oem 28.5mm, 25mm? (I want to avoid using heavier springs if not absolutely necessary to avoid the increased wear on the cams, rockers etc.) - I have yet to pull my head and measure the valve guide slop, if any, but assuming I go with new guides, any opinions on best re-fittment? I am thinking bronze guides from APE or Kibblewhite which don't require re-boring the head. The other option is using new cast oem guides which requires re-boring the head I believe. Having a shop do it either way so mainly wondering which guides are better for longevity assuming they both seal equally well. Also, can I even use oem cast guides with stainless valves? Thanks for any opinions/feedback! Neal I've attached a pic of my bike. It's a '91 with 2011 gsxr1000 front end I put on, Robby Moto triples.