QuestionQUESTION: I got to get that 305 racing bike on the road. I bought it from a florist 4 yaers ago here in salt lake city, utah, and just had the lot stored away.... because I am more into tripples (10 bikes) than honda twin.
I have extended doc that came with the race bike project but time has past and I am not sure of the priorities as far as racing it. All road parts are gone, only racing body work and racing parts are left so a restoration is out of the question. seems like the racing motor was not sold with the lot or was lost somewhere-shame- so there is 2 engine with it and one that was tentatively worked on to make it a bit performant but hardly any changes to the original short of a bore job and taking of the starter. My goal is to beat those silly britts are the larry miller track in 4 weeks. but not with and H2 Or an H1. just a little honda ( or a 350 aermacchi- I have one too).
how would the priority modification go down. I have read a lot of the doc.(the bike look a lot like the drawing on the fore page of the 1983 cb, cl72/cb,cl77 optional parts catalog)I have all the racing body parts described in that catalogue supplement. I have a brand new race seat and the speedo, the command ect. lots of secondary gear ratio combo ( that the one outside to the wheel, right?)
1- I have read that the 2nd and 3rd gear can be interchanged. whats the relevance of that and what else should be done to match that modification.
2- The brittish five speed gear box seems out of reach now that I have missed the one on ebay last years ($1800+). Is there really no way to crame in some combination of gears from other honda model to have a 5 speed? (short of external deraillor).
3- The electronic ignition or original. the motor i have doesnt have the magneto or the charging system... so that means that they used the battery direct judging by the skeleton wiring system remnants.
4- the high compression piston? .25 0ver standard, instead of the standard piston in it now and still in good condition.
5- should any work done to he head, mainly the valves?
6- I read on the forum that someone had some cb450 carbs on a 305?
I 'll post some pics of what i have next time.
thanks, JCl
One last thing.... where are you writing from.
ANSWER: Janclaude,
4 weeks isn't much time to build a race bike out of anything. My friend Tim Mings has been racing one for many years, with a basically stock motor and a portion of the YB race kit parts.
http://mercilessmingshondan600.itgo.com/
I do have the Yoshimura race document in my Restoration Guide CD for CB72-77 and other suggestions therein. If you can land a pair of the pre-65 pistons, the compression is 9.5:1 vs the 8.5:1 on the late piston sets. Megacycle Cams makes a number of cam grinds, copied from various grinders of the 1960s. You can enlarge the valves, but only one mm, so hardly worth it. There are some aftermarket options out there, like Vintage Advantage racing services in WA state.
Tim McDowell sells some forged WISECO piston kits for 305s. http://www.classichondarestoration.com/Honda-CB72-CB77/CA77/CB77/CL77-Piston-Kit
The E-ignition systems that I helped pioneer are battery operated and run off the points cam in the head. Ideally, a CDI system off the crankshaft would be more beneficial.
Just clean up any irregularities in the cylinder head ports and rough polish them.
Yes, the 2 center gears on each transmission shaft can be X'd, which closes up the ratios between 1 and 2nd gear, but opens up a big gap from 3 to 4th. There are no drop-in transmission sets available for these engines, due to the primary chain drive.
The usual old school modifications for carbs was to use a couple of CB750K0 carbs with mount adapters. I think that SUDCO makes a Mikuni conversion set for the engines now. You really don't want to go much bigger than 28mm, anyway.
Bill Silver
---------- FOLLOW-UP ----------
p 20 
p15
QUESTION: Thanks for the rapid answer.
"Ideally, a CDI system off the crankshaft would be more beneficial".
what do you have in mind? anything that i can find in a boneyard? on other models or make. I have lots of kawi H1 parts and rolling.
"but opens up a big gap from 3 to 4th'( to put the second there)
Pardon me, that means that the second becomes the third and vice versa. yes , so one of them is beneficial in the other position right? which one? the second is better in the third or the third in the place of the second... i think it means that the third is better in the place of the second but detrimental for the second to be in the place of the third because of the gap... so why not just get an extra third gear to replace the second and leave the original third gear in place... I am certain someone thought of that before etc, sorry if I sound pushy.
I am sending some scans of that booklet I received with the bike and all the doc. The front page, a page on the timing -page 15, and a page on some grinding - page 20.
That last page is pretty heavy for me. There is nothing left on my left end of the crank, thats where the magneto was, right?
So that means that they have been running the bike right out of the battery until the battery needs to be recharge.
That booklet , I thought, was giving info on putting some "Y" on a CB meaning make necessary modif to make the bike go faster.
Is that page more about changing from the 2 pistons going up together (360) to the alternate pistons up and down ( 180) the newer version?
That grinding modip should already be in place on my cb77 180 degree engine, right.
AnswerThere is nothing off the shelf for a CB77 ignition. I seem to recall that a few people had modified something from a TZ250 or similar 2 stroke twin to run off the crankshaft. I don't have details on that, however.
The grind and weld mention on the points cam is to modify a stock stator/rotor into a Energy transfer magneto system. You would have to buy some AC coils to use in that situation. You do not change the point cam profile for a normal battery operated ignition system, even with total loss power source.
The transmissions are unique in that you can swap the center gears in an X pattern and change the ratios of each pairing. It doesn't move the shift pattern. It only changes the ratio for those two gears which changes the engine rpms in those gears because of the altered gears.
You only have two choices.... a wider gap between 1st and 2nd with narrow gear spread between 3rd and 4th or the opposite... close gap between 1st and 2nd, then a wide jump between 3rd and 4th. If you put two sets of 3rd gears in the transmission, you would have 2 gears of exactly the same ratio, which does you no good at all. Study online parts illustrations to see how the center gearsets can be interchanged.
The CYB parts were Honda's attempt at making a racing kit to bolt onto the CB chassis and engine to improve performance. The factory YB camshaft has more duration, but not more lift. It will spin the motor up to about 12k, though (with YB springs), but it really isn't a good cam for a 305 displacement motor. Remember Honda whipped these parts up in 1961. When the bikes got to the US, the speed shops here found new ways to make them go faster. WEBCO made 350cc piston kits and matching roller cam kits from Kenny Harmon. All this stuff is long gone now.
Finally, the instructions you have scanned do not have anything to do with converting the engine from Type 1 to Type 2 (360) crankshaft versions. The 180 motors have less pumping losses internally than the 360 pistons which are pumping air up and down inside the cases at the same time. 180 crankshaft designs offer an air swap from side to side, so there is less internal resistance to the engine turning over at high rpms.
Bill Silver
