Quietest, cleanest engine/kit for hillclimb bike

[veloman]

I have a friend who is considering a gas engine for her folding Montague bike. She will be climbing mtns in CA, up to 5000 feet gain. (The reason she is considering gas over electric).

The most important things to her are it being as quiet as possible, least polluting, and be able to assist her up steep mtn climbs 12% + grades for 10 miles. She ISN'T looking to ride 30+mph.


Is there an ideal kit out there that would fit well on the Montague Folding mtn bike? She wants to be able to fold the bike up to store it in a camper.

Friction drive would be best right? What 4 strokes engine/kits are there for such an application? Thanks.

 

[unior]

I'd personally recommend one of the larger 4 - strokes. Dax titan (huasheng) or honda gxh50. They will be the quietest, most powerful. Gear her low for 12% grades!

 

[Skyliner70cc]

I can only see a rack mounted engine fitting easily on that frame which I wouldn't use on a steep grade going uphill...the CG would be too far rearward....She should consider a frame that would accept a Dax Titan in frame engine.

 

[kerf]

If it were me, given your criteria, I would go with this unit with a 7/8" roller.

http://www.staton-inc.com/Details.asp?ProductID=2738

 

[motorbikemike45]

I would consider a Staton inside chain drive with a Subaru Robin 35 or Honda 35 to a Nuvinci hub. Quiet and, when geared down, has gobs of torque. It is expensive and heavy, but it's also a bullet proof setup. Staton also has a 3/4 gallon fuel tank that will take her far on a fill up.

 

[motorbikemike45]

Also, sooner or later she will have to come back down the mountain, so I would use disc brakes, front and rear. Avid BB-7s should fill the bill nicely. Make sure she gets very high quality, heavy duty wheels too, especially on the rear.

 

[unior]

I don't understand why she wouldn't want a larger engine. Regardless of drive configuration?

 

[motorbikemike45]

A larger engine is heavier, louder, bulkier, the heavier rotating mass produces more vibration, gives poorer gas mileage, and is, well, larger. With a Nuvinci hub she can gear a small engine down to produce high torque for hill climbing and gear up for higher speeds on the flats while keeping revs down for quieter operation. She wants a quiet engine with the ability to climb fairly steep hills, but she isn't interested in high speed cruising. The Robin or Honda 33.5 cc engines are very quiet, meet EPA and CARB emmission requirements, give excellent fuel mileage, produce adequate power, vibrate little, and in combination with the Staton chain drive and Nuvinci hub meet all her requirements, though it is an expensive and fairly heavy set up.

The problems I see with a friction drive unit is if she is ever going to ride on unpaved trails, friction drive will not allow her to use tires with aggressive tread, and while using the smallest roller may gear the engine down enough to climb steep hills it will require very high revs with attendant noise to maintain even modest speeds on the flat.

As to the rearward center of gravity problems with a rack mounted engine/drive system mentioned above, I have climbed very steep hills (26+ degrees) with the fairly heavy Staton chain drive system with no problem. I believe the CG shift when climbing even steepish hills is so minor as to be a non issue. Should the front wheel ever start to lift, it is a simple matter for the rider to stand and lean forward to counterballance.

 

[veloman]

She only weighs 110lbs, so yeah the small engine should be enough with proper gearing.

You can ride dirt trails on a 2" tire with a slick center tread for the friction drive. You only really need knobbies if your doing real mtn biking in loose or wet terrain. I think at most she would be using this on dirt paths which would be no problem.

The staton link above looked good to me. It would fit on the folding bike - except that with any engine hanging off the side, you wouldn't be able to fully fold the bike.

 

[motorbikemike45]

I suppose it depends on which way the bike folds. If the front end folds to the left, a friction drive (engine on the left side) will limit how tightly it will fold. The Staton inside chain drive mounts the engine on the right, so if the front swings to the right when folding, it would limit how tightly it will fold. The Staton-Nuvinci set up would be ideal for her, except it is heavy enough that she might not be able to lift it into the camper. Call Dave at Staton and see what he thinks. He is far more knowledgable that the rest of us and will give the best advice, without regard for his profit. Yes, he is that honest.