Member Contributer Rush2112 Posted August 5, 2013 Member Contributer Share Posted August 5, 2013 thanks Jess, hope you are successful. beer's in it for you. Right on, Man! I've been pondering this for two years... Next round is on me! :beer: Link to comment Share on other sites More sharing options...
Member Contributer belovian Posted August 5, 2013 Member Contributer Share Posted August 5, 2013 Ok, so I texted Brian. He got back to me and said I could pass along his email address to those who wish to get in touch with him. So anyone interested can pm me for the details. Jess Link to comment Share on other sites More sharing options...
Member Contributer rangemaster Posted August 6, 2013 Member Contributer Share Posted August 6, 2013 Whoever does, please share. Link to comment Share on other sites More sharing options...
Member Contributer spinalator Posted August 6, 2013 Member Contributer Share Posted August 6, 2013 This is a little OT, but this fellow has a lot of info on boring out CB750's, one of my friends used his info and bought a kit for some big bore projects. Web Nanny filters may not allow you to access his domain, lol. http://www.satanicmechanic.org/bigbore.shtml Link to comment Share on other sites More sharing options...
Member Contributer Rush2112 Posted August 6, 2013 Member Contributer Share Posted August 6, 2013 Ok, so I texted Brian. He got back to me and said I could pass along his email address to those who wish to get in touch with him. So anyone interested can pm me for the details. Jess I don't want to swamp him with the same questions six times 'til Sunday... I suggest one person contact him and share the info. Mohawk, you want to take the lead since you have an engine in the works? CornerCarver? Bueller? Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted August 6, 2013 Author Member Contributer Share Posted August 6, 2013 Well if we put together some specific questions then we can get Jess to send him one email ! And hopefully leave the man in peace :) So with that in mind, I need to know the following. 1. Do you know how thick the MMC liners are ? 2. What is the maximum overbore you used keeping the MMC, if you did this ? 3. What did you go to achieve the 870cc big bore ? For example Steel liners / Nikasil etc ? 4. What did you do for head gaskets ? That's all I need to know. If anyone else, has any SPECIFIC questions, then add to my list. Thanks Jess. Link to comment Share on other sites More sharing options...
Veefer800Canuck Posted August 6, 2013 Share Posted August 6, 2013 For the head gaskets, someone posted a link earlier for a place that makes custom copper head gaskets. With the gear drive cams, Im gonna say that the gasket thickness will have to exactly match the OEM gasket. If you gave them the upper crankcase, the cylinder heads, and a sample OEM gasket, I'm sure they could bang a couple out. Link to comment Share on other sites More sharing options...
Member Contributer Rush2112 Posted August 6, 2013 Member Contributer Share Posted August 6, 2013 Well if we put together some specific questions then we can get Jess to send him one email ! And hopefully leave the man in peace :) So with that in mind, I need to know the following. 1. Do you know how thick the MMC liners are ? 2. What is the maximum overbore you used keeping the MMC, if you did this ? 3. What did you go to achieve the 870cc big bore ? For example Steel liners / Nikasil etc ? 4. What did you do for head gaskets ? 5. What pistons and rods did they use? Were they Honda parts bin stuff (i.e. CBR 929, 954, 1000 parts) or after market? 6. Any stroker cranks involved? If yes, what rod length and pistons used and where to get the crank stroked & balanced? Any recommended machine shops? That's all I need to know. If anyone else, has any SPECIFIC questions, then add to my list. Thanks Jess. I would like to add 5 & 6. Also, on #4 head gaskets, I think someone posted up that Cometic will make MLS custom gaskets just send them a set of originals and they will use it as a template and increase the cylinder bore diameter to fit the application. Link to comment Share on other sites More sharing options...
Member Contributer belovian Posted August 6, 2013 Member Contributer Share Posted August 6, 2013 I've sent Brians email address to rush and mohawk. that should get the dialog going. Jess Link to comment Share on other sites More sharing options...
Member Contributer spinalator Posted August 6, 2013 Member Contributer Share Posted August 6, 2013 I bought Brian's Corbin seat for my 95 sometime in the early 2000's. I was considering the big bore and then moved to Ireland for a year and blew all my savings. Hopefully you guys can get this figured out, I am watching the developments! Link to comment Share on other sites More sharing options...
Member Contributer CornerCarver Posted August 7, 2013 Member Contributer Share Posted August 7, 2013 Been out of town for business...Rush added the only two additional questions I could think of re: stroking the RC46 engine. So, have Rush or Mohawk contacted Brian yet? Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted August 7, 2013 Author Member Contributer Share Posted August 7, 2013 OK, I've complied the questions in a polite email just sent them to Brian. Watch this space for updates. Link to comment Share on other sites More sharing options...
Member Contributer YoshiHNS Posted August 7, 2013 Member Contributer Share Posted August 7, 2013 Cometic should be able to make a custom gasket out of copper and possibly out of their MLS stuff. I like the composite stuff a bit better, as it's that little bit soft to make sure you have a good seal, whereas the MLS stuff you have to have your block and your heads flat within 0.001". On the GT, my block was perfect, but my head was out 0.004" (which is still within OEM spec), and the MLS gasket leaked like a sieve. Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted August 7, 2013 Member Contributer Share Posted August 7, 2013 As a serial VFR big bore kit owner (see sig...), I am always interested in ways to throw money I don't have at problems that don't exist. Count me in! I think my supercharged 5th-gen really needs an 870cc engine...or maybe a 900? Say "hi" to Brian for me...I think I still owe him a beer! Ciao, Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted August 11, 2013 Author Member Contributer Share Posted August 11, 2013 OK, so here's my email to Brian, followed by his reply;- Hi Brian, I hope you are well, please excuse this intrusion. Jesse off the VFRD forum gave me your email address, so that hopefully you can answer some questions about the VFR800 Big Bores that Dynamo Hum used to do. Myself & another forum member have a couple of spare engines & have been working on a big bore VFR plan. I have info from TTS in the UK, that the VFR800's MMC liners can be safely bored to 74mm & nikasil coated. Although according to Honda they can be bored & honed as normal provided the temperature is kept low ! You may have experience in this area, please feel free to elaborate. The basic options I have investigated are either a 74mm bore using CBR929 pistons giving 825cc, or a 75mm bore using CBR954 pistons giving 848cc. I assume the dynamo hum 870cc was a 76mm bore, so this has lead to the following questions. 1. Do you know how thick the MMC liners are ? (std bore=72mm + 8mm cylinder wall thickness) 2. What is the maximum overbore you used keeping the MMC, if you did this ? 3. What did you do to achieve the 870cc big bore ? For example Steel liners / Nikasil etc ? 4. What did you do for head gaskets ? 5. What pistons did you use? Were they Honda (i.e. CBR 929, 954, 1000 parts) or after market? 6. What rods did you use? Were they Standard or after market? I assume that question 7 is self evident as a NO, due to the gear cams, but the other builder has asked, so here it is. 7. Any stroker cranks involved? If yes, what rod length and pistons used and did you have to get the crank rebalanced? Many thanks for taking the time to answer these questions from us crazy fools :) Regards Chris Walker ============================================================================================ Hi Chris Sorry for the slow reply. I will try to answer your questions as best I can. I think I destroyed all the technical information in a drunken purge. I developed the 800 big bore kit with the help of a talented mechanic and JE Pistons (now called Sportsman I think). At the time we were trying to figure things out Honda was no help whatsoever. The liners were new and Honda didn't want to provide any information. No stroker for the 800. We thought about nikasil but rejected this approach. JE helped us design new pistons and we went with steel liners pressed in. When I gave up Dynamo Humm I gave up my rights to the vfr750, 800, and vtr1000 pistons. You should be able to buy just one set at a time. They come with rings and wristpins. Lighter and stronger than stock. Slight raise in the compression ratio. Ran fine on super gas. The stock rods and crank were lightened, balanced, and polished by Falicon. Because the pistons were a custom order for us we were obliged to buy a minimum of 24 at a time. This allowed us to further balance everything by weighing the pistons, rings, wristpins, and rods. The head gaskets are stock Honda carefully and meticuosly hand made using a dremel tool. A couple of hours for each set. The first motor had a design flaw in the pistons and one was hitting the head and eventually cracked it. The second motor had a badly pressed in liner that caused that motor to go BANG ! The third one blew a head gasket and overheated. Fourth and subsequent motors were trouble free. I put about 50,000kms on mine. Hope this helps .... crazy fools rule Brian Link to comment Share on other sites More sharing options...
smythie Posted August 11, 2013 Share Posted August 11, 2013 Crazy fools rule. :lol: Link to comment Share on other sites More sharing options...
Member Contributer spinalator Posted August 11, 2013 Member Contributer Share Posted August 11, 2013 Steel liners, interesting. Link to comment Share on other sites More sharing options...
Member Contributer CornerCarver Posted August 11, 2013 Member Contributer Share Posted August 11, 2013 thank you so much Jesse, Chris and especially Brian for the information! I hope I am not reading too much into his response but the line about Honda being no help with answers (especially on the MMC liners) would point to not knowing at the time that they liners could be re-honed and re-used provided that they were bored (as we now know 10 years later) slowly to control heat...maybe they would have selected steel liners regardless.... The engine I am building is going into a V7 heavyweight club racing bike and anything 750 and over get lumped together so the more CC's the better for us (as long as it holds up for a season of endurance racing). So 76mm bore and a probably steel liner for us, I may still inquire about stroking the engine and see if any stock CBR rods match the necessary shorter length for a stroker engine. I am hoping my biggest problem is how to build a 7.5 gallon fuel tank from a spare 6th gen tank. probably not though... Link to comment Share on other sites More sharing options...
Member Contributer belovian Posted August 12, 2013 Member Contributer Share Posted August 12, 2013 Glad I could help! I spoke this week to that very talented mechanic Brian was referring to, Bruce Allnut. I stopped by his recently opened shop to chat about all things two wheeled and plied him with a few questions about the big bore kit as well. He essentially mirrored what Brian said, but added a few details. Like on a couple of the engines he remembers removing a set of gears. I believe he was talking about the gears the keep tension on the cam drive gears to quiet them down. said it added some noise but really helped "wake em up". He remembers with quite a bit of detail a lot of the processes involved. If you guys have any other Q's fire away and I'll ask him too!! Jesse Link to comment Share on other sites More sharing options...
The Phantom Posted August 12, 2013 Share Posted August 12, 2013 Like on a couple of the engines he remembers removing a set of gears. I believe he was talking about the gears the keep tension on the cam drive gears to quiet them down. said it added some noise but really helped "wake em up". Yes the guys racing VFR400s in the Clubman class over here have been doing that for years, sounds like someone has emptied a bag of nails into the valvegear at idle but the reduced rotating mass certainly helps them to rev. I took them off the cams in my 750 for the same reason, but it's not a simple job as the scissor gear assembly is pressed/riveted into place. Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted August 12, 2013 Author Member Contributer Share Posted August 12, 2013 I may still inquire about stroking the engine and see if any stock CBR rods match the necessary shorter length for a stroker engine. You can't stroke the 800fi, the gear cams preclude this, it was already stroked 2mm by Honda taking the RC45 750 to 781cc in the 800fi. Every stroker I've seen has seperate barrels so that you can add stroke at the base gasket. The VFR's don't have a base gasket, as the bores are cast into the upper crankcase & the bearing webs intrude into the base of the bore, so you can't make the psitons travel further. That said the 954 piston is about 6mm shorter than the 800's so you could play with the crank & rods within that limit, but I don't know if there would be enough deflection angle to accomodate the extra stroke &/or enough crank web to relocate the bigends with enough meat left to deal with the forces. A quick calc shows a 75 x 54mm stroke engine would give 953cc, if you could get a 76mm bore then it would give 979cc with the potential for 140+rwhp. Good luck with the huge dollar expense of that one. Link to comment Share on other sites More sharing options...
Member Contributer YoshiHNS Posted August 12, 2013 Member Contributer Share Posted August 12, 2013 Got a write up or other info on that mod? Link to comment Share on other sites More sharing options...
CandyRedRC46 Posted August 16, 2013 Share Posted August 16, 2013 what about stroking the vtec engine? Link to comment Share on other sites More sharing options...
JES_VFR Posted August 17, 2013 Share Posted August 17, 2013 Glad I could help! I spoke this week to that very talented mechanic Brian was referring to, Bruce Allnut. I stopped by his recently opened shop to chat about all things two wheeled and plied him with a few questions about the big bore kit as well. He essentially mirrored what Brian said, but added a few details. Like on a couple of the engines he remembers removing a set of gears. I believe he was talking about the gears the keep tension on the cam drive gears to quiet them down. said it added some noise but really helped "wake em up". He remembers with quite a bit of detail a lot of the processes involved. If you guys have any other Q's fire away and I'll ask him too!! Oh, Oh I know this one.... As a former RC51 owner I know this trick. The gears Bruce is referring to are called quieting gears (or silenceing gears) and maintain what is called a zero backlash drive in the cam gear drive. What they are is a spring loaded second gear that keeps pressure on the back side of the gear faces. That keep them quiet and relatively rattle free as well, but adds a bit more friction to cam gear drive. Removing it frees up the gears and they all spin much easier as well as removing a bit of weight ( 15 ounces of rotating weight on each cylinder of the RC51). Sure it allows a tiny bit of backlash (.015 degrees of play at the camshaft on the RC51) to occur any time you violently decelerate the engine, but how often does that really happen??? About the only downside on a Street bike is that the gear driven cams will now clatter quite a bit. On the already loud RC51, it sounds a lot like you somehow added a vented dry clutch. I don't now how much louder it would make the VFR sound, but I'm not rushing to remove them on my street bikes. But those that are thinking of racing, might want to do this "free" mod. Link to comment Share on other sites More sharing options...
CandyRedRC46 Posted August 17, 2013 Share Posted August 17, 2013 Cool stuff. Makes me wish I had gear driven cams. Link to comment Share on other sites More sharing options...
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