honda305 Home honda305 Auctions honda305 Gallery honda305 Forum Forum

□ Search
□ FAQ 
Vintage Honda Owners,
Restorers, Riders and

Modification ideas - welcoming commments

Post Reply
goodfeste Member
Posts: 3
Joined: Mon May 12, 2008 8:51 pm

Modification ideas - welcoming commments

Post by goodfeste » Sat May 17, 2008 12:32 pm

Glad I discovered this forum online. Sounds like some real nice folks on board. It's getting harder each year to find Honda 305 enthusiasts here in southern California. My favorite 305 is the Dream. I owned one in the late 1970's (a black 1967 in good original shape) and hope to find another soon.

I'd like to keep that next Dream entirely stock but possibly modify the 305cc engine. Questions:

1) When I owned my previous Dream, I also owned a new Honda CM400T Custom which had the smoothest 4-stroke twin cylinder engine. I was told it was "counterbalanced." What does that mean? I've heard of race car engines getting "balanced and blueprinted." Same thing? Could it be done to the 305 engine?

2) Would a 305 Super Hawk's 180 degree crankshaft swap into a Dream engine? I can see that the Dream's single carb, cylinders and intake stuff would have to remain, to properly fit the frame. I believe that the result would be less torque at low revs -- but real Super Hawk mid and high-end revving. However, there's still that single carb. Possible to re-jet it?

3) When I was a kid in the 1960's and Dreams were showroom new, bike magazines often advertised "big bore kits" to convert, for example, a 90cc engine into a 100cc, or a 160cc to 175cc. It's got me wondering if anyone out there has ever installed a big bore kit on a 305 engine (say, to 350cc)?

Thanks everyone, for whatever information and wisdom you can provide. And thanks for a great forum.

User avatar
davomoto Member
Posts: 2508
Joined: Sat Nov 18, 2006 7:36 pm
Location: Marin County CA

Post by davomoto » Sun May 18, 2008 12:02 pm

Not possible to ad a counterbalancer. It is basically a wieght, on a shaft, with a chain, that is timed to counter effect the weight of the crankshaft. Webco used to offer a 350 kit, but hasn't for a long time. The 3mm overbore kits come up on ebay from time to time. I don't know what the effect of a 180 crank would be as far as performance. In my, and many others on the forums opinion, you are much better off leaving the engine in it;s stock, and reliable condition. These are 40 + year old technology, and need to be appreciated for what they are. That said, good luck with your search, and welcome to the forum!


goodfeste Member
Posts: 3
Joined: Mon May 12, 2008 8:51 pm

To Modify or Not to Modify

Post by goodfeste » Mon May 19, 2008 12:59 am

Thanks for the rapid replies to my ideas about counterbalancing the 305 Dream engine, use of a 180 degree crank vs. 360 degree crank, bore-out to 350cc, etc.. I can see where the counterbalancing is out of the question, and the 350cc bore-out might leave the cylinder walls a bit thin for comfort.

But I still wonder about that 180 degree chrankshaft. Seems plausible to me that somebody somewhere out there cobbled back together a derelict 305 -- say, a Dream -- but installed an engine from another model, say a Super Hawk. Hmm. I just wonder.

My primary reason for considering engine modifications is that I live in southern California where people routinely drive like maniacs: 50mph on the streets, 75mph on the freeways. So, some kind of like speed is desirable. I used to live near the Canadian border where there are some great 50mph scenic rides, perfect for a 305 Dream. Down here I wouldn't take a Dream on our freeways for long because it's a bit small for that environment. Perhaps the easiest and cheapest way for my future Dream to keep up with various southern California traffic might be if I just change to a slightly larger counter sprocket (or slightly smaller rear wheel sprocket) so that the engine wouldn't be revving quite so much at speed. Comments?

I really appreciate this forum and hope you folks don't mind that I get things off my chest. Much of my 305 ruminatin' has been in my head literally for decades because, until now, I've not been able to locate any others to discuss with any practical knowledge.

Last item: when I owned my 1967 305 Dream, I found and installed a strange windshield. Don't recall if it was OEM. The upper section was the plexiglass shield. But the lower section was like a waterproofed canvas. It attached at various points around the headlight nacelle and handlebars, and hung sort of limp. But at speed, the force of the wind made it taut. Well, I doubt that such a windshield is available anymore but I do wonder if anyone knows of a nice looking Harley-style windshield (not tall) that can be modified to fit the Dream's square headlight nacelle and looks like it belongs there. In other words -- what do you folks who want a windshield, use?

Thanks for your patience with my questions and comments.

Post Reply


CB-77 | CYP-77 | Road Test | Riding Log | Literature | Zen | Marketplace | VJ Survey | Links | Home