De-tuning a Supermini for pump gas.

[justalonewolf007]

Suddenly, I've had a 2005 Honda CR 105 fall into my lap.

Can't say no for the price, but it has been set up for, and runs 110 race fuel. The highest availible octane in my area is 93, and in my town is 91 (maybe 92) unless I really missed something.

I'm only slightly mechanically inclined. But porting is way over my head.

Can it be de-tuned without buying a new jug and having it re-bored and ported?

:whoa:

 

[Chili]

The head will need to be modified or replaced, the jug doesn't need to be touched. Since it's a big bore even replacing it with a stock CR85 head will still end up with the head likely needing mods. I'd pop off the head and send it over to Eric Gorr and let him tell you if this one can be returned to using pump or if you'll need a new head.

No thoughts on acquiring race fuel and running as it was setup?

 

[justalonewolf007]

I had thoughts of using race gas, but also thought the nearest race fuel station was over 3 hours (more like 5) away.

However, thanks to some good detective work by a few friends. I was directed to a gas station only 1/2 hour away! My internet searches had turned up nothing. Technology is winning today I guess.

I am, however, thinking that the head would still need modification - as I believe that the bike is set up for a much more skilled rider than I am. I will save up a few extra bucks and send things Eric's way so I will hopefully, finally, end up with a bike that is actually set up for me!

Costwise, I am not sure that I will save much within a season or two by purchasing a new head (73 bucks) with about 150 or 200 for Eric's work (I have to re-look up the information) and having it set up for pump gas as well as better low end.

Thanks for the input Chilli! You guys rock :)

 

[Chili]

I can't say for certain but I doubt a simple head rework will cost you that much.

 

[Rich Rohrich]

It's important to keep in mind that if the cylinder is ported for high rpm power, it's likely you won't be able to "undo" it. Modifying the head to run on pump fuel isn't normally a big deal. Unporting a heavily modified cylinder is another matter entirely

Just something to consider.

 

[Pete Payne]

Call cometic gasket company. have them make you a 1mm thick head gasket . The head gasket that is on it now is probably.25mm .

Have you even done a compreesion check ????

 

[Ol'89r]

You could also try adding an extra head gasket. Go to your local auto parts store and buy a can of Copper Coat spray. Spray both gaskets completely with the spray and install the gaskets while the spray is still tacky. This would be an inexpensive way to see if lowering your compression will help.

 

[helio lucas]

+1 in thick base gasket... if the bike is stock and only the bore is bigger it will do a good work in over rev and take a little the snap from mid range...

 

[justalonewolf007]

I shouldn't have worried - The test ride, as brief as it was, left me grinning hugely.

It felt like riding a 4-stroke, only better. The power was "right now" unlike my old 80, which was "c'mon c'mon c'-Wheeeeeelie!!!" The power comes on right NOW!

Later on, after I get some more saddle time, I will decide whether or not to try mod it for other tendencies.