Honda CBR250R, upgrade to 305cc with Takewaga

[soapie'schoice]

     Nice scoot... Unfortunately the hot cam/stock displacement may turn out to be slower than stock.. A modified vehicle works best as a well thought out combination. The added lift/ duration of the hotter cam was  apparently well matched to the bigger bore. With additional duration and again with the smaller bore means you will not have the bottom end torqure that you had stock.. In fact many times adding a hotter cam without other mods such as more compression ,or displacement to compensate , you could actually make it slower that stock, and a not fun bike at all. Other than doing it the right way with a maged and balanced bottom end, and the 305 kit, think it is time to look at something more suited to your riding style.  Also, you may have to re- remap the thing going back to less cc's.

[MalcolmT]

the honda  500  is a nice big bike, comfy to ride,even for the pillion.about 50bhp so no  monster but will we of the 300 without needing to be thrashed.

 

[td5855]

On 2017-6-3 at 2:03 PM, soapie'schoice said:

     Nice scoot... Unfortunately the hot cam/stock displacement may turn out to be slower than stock.. A modified vehicle works best as a well thought out combination. The added lift/ duration of the hotter cam was  apparently well matched to the bigger bore. With additional duration and again with the smaller bore means you will not have the bottom end torqure that you had stock.. In fact many times adding a hotter cam without other mods such as more compression ,or displacement to compensate , you could actually make it slower that stock, and a not fun bike at all. Other than doing it the right way with a maged and balanced bottom end, and the 305 kit, think it is time to look at something more suited to your riding style.  Also, you may have to re- remap the thing going back to less cc's.

You are correct, since I have had it back there is poor lowdown torque, a lot less than before.  Only compensation is that the cams do allow the engine to spin very quickly above 8500rpm.  

So you are correct, I should have had the standard cams refitted and had the enjoyment of going around without thrashing it.  Cannot put back the original fuel control system since the O2 sensor is gone on the new big bore exhaust.

Only option I will take is to refit the BBK kit but this time do the rebuild myself.

[soapie'schoice]

Yeah, I was afraid that would be the result... Also, I HIGHLY suggest when you do a big bore, that you get a GOOD balancing job done. 99 times out of a hundred it seems, people add a bigger piston, heaving rings and pins,and end up with a machine that vibrates like one of those inexpensive Chinese massaging tools. this is not good for the longevity of your investment...however ,like the Chinese massager, in many cases it will vibrate long enough to you to get screwed...And not in a good way. Take some time and build it right, with cleanliness, proper assembly techniques and tools. balancing, proper ring fitting,(I suggest file fit rings, if available), the correct honing method , tunining and break-in. With these ideas in mind, you can end up with a smoother, much more enjoyable machine. The bigger bore will give it a nicer feel, without revving the piss out of it. RPM is what kills engines. Without going into complicated math, know that an extra 400-500 revs can reduce engine life by as much as twenty, yes 20 percent, or more. .Try to find knowledgeable people that have experience with your machine... Ask around, make calls, emails. Get good advice. Even if you have to ship parts to Japan, or someplace else, having the right work done is like money in the bank if you plan on enjoying your scooter for a long time. Best of luck. Did not realize this would more than a sentence or two when I began.. Sorry about that.

[td5855]

16 hours ago, soapie'schoice said:

Yeah, I was afraid that would be the result... Also, I HIGHLY suggest when you do a big bore, that you get a GOOD balancing job done. 99 times out of a hundred it seems, people add a bigger piston, heaving rings and pins,and end up with a machine that vibrates like one of those inexpensive Chinese massaging tools. this is not good for the longevity of your investment...however ,like the Chinese massager, in many cases it will vibrate long enough to you to get screwed...And not in a good way. Take some time and build it right, with cleanliness, proper assembly techniques and tools. balancing, proper ring fitting,(I suggest file fit rings, if available), the correct honing method , tunining and break-in. With these ideas in mind, you can end up with a smoother, much more enjoyable machine. The bigger bore will give it a nicer feel, without revving the piss out of it. RPM is what kills engines. Without going into complicated math, know that an extra 400-500 revs can reduce engine life by as much as twenty, yes 20 percent, or more. .Try to find knowledgeable people that have experience with your machine... Ask around, make calls, emails. Get good advice. Even if you have to ship parts to Japan, or someplace else, having the right work done is like money in the bank if you plan on enjoying your scooter for a long time. Best of luck. Did not realize this would more than a sentence or two when I began.. Sorry about that.

I can do all the strip down and rebuild work myself, my first engine rebuild I did were on BSA C15, then Honda twins in the 70's.  First major project (Production class 250) were mixing and matching a Yamaha YDS7 bottom end and g/box to RD barrels, which had all the ports opened up to max, that you had to change the rings after every 3rd meeting, (Found that out the hard way) inlet ports were bored out to take the 28mm carbs from the RD350, stock mikunis 26mm.

Spent all my life on ships or semi submersibles, 1977 to 2015 so enjoy getting the spanners out.  Attached is a photo of my first race bike.  It had a twin leading drum shoe at the front.  Anybody remember them??

Take care Soapie.

[soapie'schoice]

Sounds like you know what you are doing...obviously, not your first rodeo. Don't know how many times I have tried to answer younger people's questions about performance , only to have hard won advice totally ignored. Probably you have had similar experiences. . Coming from the days of Powroll, Webco, Denco, Yoshi etc.. seen more than one failed hop up ..Even had professional race team people pooh-pooh , much to their displeasure. Took them 3 points race failures to seek outside advice.. never got an apology, or thank you. You don't  need my advice. Love to hear more when it is up and running.