Gixxus Christ! Posted July 8, 2014 Author Report Share Posted July 8, 2014 My dad found a set of 29 mm mikuni smooth bore carbs in the loft of his garage...These are what guys were putting on their modified 750's back in the day. Gonna need a full rebuild but should be worth it, these carbs make serious power over the stock kei hins....pics to follow. ... Quote Link to comment Share on other sites More sharing options...
redkow97 Posted July 8, 2014 Report Share Posted July 8, 2014 This bike was chewing up most hardly ablesons with the stock motor...now I'm just going to embarrass them.... Isn't that the case for virtually any Japanese inline 4? I love the torque of V-twins, but I think the I-4 has proven itself to be superior, if not quite as simple. Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 8, 2014 Author Report Share Posted July 8, 2014 It's more the design of the v twin. Victory makes an incredible motor. 100 hp and like 90 ft of torque. That's out of a 100+ inch motor tho. It's got a 4 valve head and ohc iirc...vs 2 valve head and push rods for hd. You can squeeze huge power out of a twin, that new American v twin sport bike the ebr or whatever makes like 180 hp from an 1190cc twin. Pretty impressive...but put a turbo on a zx1200 and tune it properly and it makes 507 hp. I4 has definitely got more potential for growth because you have more pistons, crank, rods etc to spread the load over but talk to anyone who's owned a tl1000, aprillia rsv, ducati panigale etc and they'll tell you that v twin can make some serious power. Quote Link to comment Share on other sites More sharing options...
ReconRat Posted July 8, 2014 Report Share Posted July 8, 2014 (edited) My dad found a set of 29 mm mikuni smooth bore carbs in the loft of his garage...These are what guys were putting on their modified 750's back in the day. Gonna need a full rebuild but should be worth it, these carbs make serious power over the stock kei hins....pics to follow. ...Those sound small for what you are doing. I thought a 900cc would be up around 35 to 38 bore Mikuni.I thought 29mm or 30mm was more like what my CB550F has. here's a casting number list for the carb bodies. Might find it on the list.:http://www.motorcycleproject.com/motorcycle/text/specs.html Edited July 8, 2014 by ReconRat Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 8, 2014 Author Report Share Posted July 8, 2014 Turns out they aren't the 29 mm carbs...they're 28. Cb750 came stock with 28mm, 500 and 550 had 26 iirc. The mik 28mm will still breathe better because it's a smooth bore. 38mm would be way too big. My bandit 1200 has 36mm carbs. Gsxr1100 had 38. Bigger displacement doesn't always work better with bigger carbs, like any other tune, you have to optimize it for something. For example, a smaller throat carb will deliver better low and midrange power due to higher velocity venturi effect from a smaller throat, but loses flow efficiency at higher rpms. A bigger carb will have less velocity down low but will flow more cfm up top. Cam profile dictates a lot about carb choice. A milder street cam will benefit from a smaller carb for ridability on the street. A high lift, high duration cam will be pretty worthless on the midrange but will benefit from a larger carb that flows efficiently at the rpm that the cam starts to run efficiently. The cam I put in this motor isn't crazy, but is significantly longer and higher than stock and would have really loved the mikuni 29 mm smooth bores...but the 28's will still out-flow the stock keihins. I'd really like to fit a set of keihin CR carbs, or find a rack of 30mm CV carbs that would line up without too much modification. Another option would be to gut my carbs and de-rack them, then chuck them on a lathe and indicate them perfectly on center and bore a mm or two out of the throats. There's enough meat there to do it and the slides are large enough to still function correctly....and I have access to a lathe....it's just a fucking ton of work. Quote Link to comment Share on other sites More sharing options...
smccrory Posted July 9, 2014 Report Share Posted July 9, 2014 How on earth did you learn how to do that? Quote Link to comment Share on other sites More sharing options...
ReconRat Posted July 9, 2014 Report Share Posted July 9, 2014 Agreed then. Especially about the flow rates for the purpose. I looked up my Yoshimura stuff for the cb550f. It said use 28mm Keihin (cb750) on the cb550. That must have been what I was thinking. But I really like the stock Mikuni smooth bores better. I just like Mikunis in general. Quote Link to comment Share on other sites More sharing options...
bigd Posted July 9, 2014 Report Share Posted July 9, 2014 Congrats man, this was awesome to read through. Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 9, 2014 Author Report Share Posted July 9, 2014 Smc, do what? Quote Link to comment Share on other sites More sharing options...
smccrory Posted July 9, 2014 Report Share Posted July 9, 2014 Smc, do what? I'm just highly impressed with your knowledge of carbs, is all. How'd you pick that knowledge and experience up? Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 9, 2014 Author Report Share Posted July 9, 2014 I work on a lot of bikes, most of them carbureted. I research and soak up whatever info I can find on them. Of the 9 bikes I've owned, 8 were carbd, so I kinda had to learn. Quote Link to comment Share on other sites More sharing options...
Helmutt Posted July 10, 2014 Report Share Posted July 10, 2014 Bike sounds good Sam, throttle response appears to be nice and snappy. Been a long time coming Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 10, 2014 Author Report Share Posted July 10, 2014 Rode it the other day, gonna need jetted. Pulls ok low but mid and high are anemic. Quote Link to comment Share on other sites More sharing options...
gsxkat1100 Posted July 10, 2014 Report Share Posted July 10, 2014 Next time you get it out, you should stop by. I want to see how much better it looks out in the sun. Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 10, 2014 Author Report Share Posted July 10, 2014 Ok...still no tag and the back tire is bald but I might bring it by today depending on what else I have going on. Need to finish a brake job on a goldwing and then I'm sure momma has something for me to do Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 29, 2014 Author Report Share Posted July 29, 2014 Hooned around the neighborhood a d noticed that my front brakes were nearly worthless. Ordered a rebuild kit and tore down the master cyl...what a mess. All the rubber was shot and everything was full of nasty brown brake fluid, rust and dirt...probably the oem guts from '72. Rebuilt it today, should have brakes tonight. Also gonna get a tag and locate a tire and this job is in the bag. Quote Link to comment Share on other sites More sharing options...
gsxkat1100 Posted July 29, 2014 Report Share Posted July 29, 2014 What size tire do you need? My spare set is going on the 550 soon and the ones that are on it are still good. Changing them because of where I work.... Quote Link to comment Share on other sites More sharing options...
max power Posted July 29, 2014 Report Share Posted July 29, 2014 So where are the after pics? Quote Link to comment Share on other sites More sharing options...
redkow97 Posted July 29, 2014 Report Share Posted July 29, 2014 What size tire do you need? My spare set is going on the 550 soon and the ones that are on it are still good. Changing them because of where I work.... was going to ask the same. I have a take-off Q2 in my garage that you can have. I'm sure it's too wide, but if it will fit, it's safer than a bald tire! Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 29, 2014 Author Report Share Posted July 29, 2014 100-90-19 front and 120-90-18 rear. I think I also have a spoked 17" rear wheel somewhere I could use if someone has a 17" tire.Even if the tires aren't worn or dry rotted, if they're older than 5 (I think) years they've lost most of the oils in the compound and are probably too hard to use safely. Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 29, 2014 Author Report Share Posted July 29, 2014 After pic of rebuilt master cyl. Nick, upload the pic you took of the guts we pulled out last night to photobucket and then post the img link on here....or send me the pic if you don't have a photobucket. Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 29, 2014 Author Report Share Posted July 29, 2014 The old guts. Notice the brown sludge... Quote Link to comment Share on other sites More sharing options...
Gixxus Christ! Posted July 3, 2015 Author Report Share Posted July 3, 2015 Ah grave digging....Bike is nearly complete. Got seat back from upholsterer today....not thrilled but for what I payed I can't bitch. Tank and side covers are being painted, should be done soon. Went with a black base coat and a titanium pewter pearl mid coat which results in a deep gunmetal with lots of pearl and metal flake effects. Ordered new black bullet blinkers with finned covers, a bikini fairing for the headlight, some tec adjustable remote reservoir shocks, rebuilt the forks and stiffened them up a bit and improved the damping. Got the custom gauge completely sorted out, brought the fuse box and charging system into the 21st century, drag bars, new master cyl, started blacking out all the chrome with plasti dip. Will shitcan the rear fender and replace with a fiberglass bobbed unit from carpy's cafe. Few weeks and it Will be on the road. Quote Link to comment Share on other sites More sharing options...
smccrory Posted July 3, 2015 Report Share Posted July 3, 2015 (edited) Nice! Looking forward to the pictures. Edited July 3, 2015 by smccrory Quote Link to comment Share on other sites More sharing options...
max power Posted July 3, 2015 Report Share Posted July 3, 2015 Tell me you kept the king/queen seat!? It's too weird to die! Quote Link to comment Share on other sites More sharing options...
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