Honda Rebel Forum banner

21 - 40 of 41 Posts

·
Super Moderator
Joined
·
29,293 Posts
That jet sure doesn't look anything like the stock jet, but it might be OK. You can order any size jet from a variety of places. Just be sure to specify a Keihin type jet, because Mikuni jets won't fit your Keihin carb.
 

·
Super Moderator
Joined
·
29,293 Posts
Be tween Keihin and Mikuni? They are two brands of carburetor, and just like Chevy and Ford parts, they are brand specific as far as fit.
 

·
Premium Member
On 2 wheels: 1998 - Rebel 250, 1980 - CB125, 1982 - CM125, 1980 - CM200, 1987 - Yamaha FZ750
Joined
·
17 Posts
Dual carbs expensive?
Depending on what quality you want, you can get a dual carb, an intake-manifold(pair), and dual-to-single airfilter-adapter for U.S $ 50 incl. shipping from AliExpress.
You do NOT have to change camshaft or other parts, for converting to duals.
If you want a new euro-camshaft, it is getting more expensive:
Or have the stock re-ground.
But it is not needed / necessary
The original air-filter, however, is a restriction. (K&N is better, probably other brands too, that does not have the "internal-metal-tube")
Also the filter- box is restrictive, it will need a few additional 1/2" holes ...(or use someones "educated" fantasy)
 

·
Premium Member
On 2 wheels: 1998 - Rebel 250, 1980 - CB125, 1982 - CM125, 1980 - CM200, 1987 - Yamaha FZ750
Joined
·
17 Posts
Keihin and/or Mikuni (and chinese replicas) are just carburettors, as "dum" as a Holley, Weber, QuadraJet, Carter, Edelbrock, Dellorto, (and I have been running all these on a Ford SB)
None are special or better, before you get into the "race-only" versions. The largest difference is in getting parts, and jets...
 

·
Premium Member
On 2 wheels: 1998 - Rebel 250, 1980 - CB125, 1982 - CM125, 1980 - CM200, 1987 - Yamaha FZ750
Joined
·
17 Posts
BTW, I'm born HOT-RODDER, I see opportunities, not problems...
 

·
Super Moderator
Joined
·
29,293 Posts
The original air-filter, however, is a restriction. (K&N is better, probably other brands too, that does not have the "internal-metal-tube")
Also the filter- box is restrictive, it will need a few additional 1/2" holes ...(or use someones "educated" fantasy)
While the K&N and similar filters allow more airflow, they also allow more dust and fine grit into the engine. Several forum members have switched to more open filters. Some report increased power as measured by their "butt dyno", and some say there is no noticeable change. But to my knowledge, no one has actually done a pre and post filter change dyno test to settle the issue. Increased airflow in a larger engine can significantly increase horse power, but on a small engine like the Rebel's, there will be little, if any performance gains, and, as pointed out above, some drawbacks. Ditto for drilling holes in the airbox, which also has drawbacks.
 

·
Premium Member
On 2 wheels: 1998 - Rebel 250, 1980 - CB125, 1982 - CM125, 1980 - CM200, 1987 - Yamaha FZ750
Joined
·
17 Posts
I did not say K&N was the best filter, I tried to make out a point with the stock filter.

If changing anything is so bad, why do you not just tell all users to never start, or use their bikes...?
Or worse, getting close to the bike with a tool in hand?
 

·
Super Moderator
Joined
·
29,293 Posts
I did not say K&N was the best filter, I tried to make out a point with the stock filter.

If changing anything is so bad, why do you not just tell all users to never start, or use their bikes...?
Or worse, getting close to the bike with a tool in hand?
I never said no one should modify their ride, and I don't recall ever saying they should never start, use their Rebels, or get close to the bike with tools. I believe my statement highlighted in red below inherently involves using tools, starting the bike, and riding it.

I'm not sure resistance is the correct term. For the non-Aussie/Asian bikes, going with dual carbs involves sourcing the correct intake and buying the dual carbs, which isn't cheap. Ditto for the internal engine mods, especially if you have to pay someone else to do them. Wjmrty is an accomplished mechanic/machinist with the skills and equipment needed to do those modifications. If someone wants to modify their engine for more power, I say go for it. But for the average rider, it's just easier and cheaper to get a bike with more power from the factory than try to boost the CMX250 engine to its potential maximum. Possible and practical mean different things to different folks. Can't find the link, but Honda made a one off 250 that made ungodly amounts of power on the track. Think it still holds the records in its class. But they had the engineers and resources to make that happen, and cost wasn't a consideration.
What was your point with the stock filter? That it is more restrictive than a K&N type filter? Did I say that wasn't true? Did you mean there will be improved performance with a more open filter? If yes, what evidence do you have to back that up? Would it then follow that running an engine without any filter, which would be even less restrictive than the K&N type filter, would provide even more power, and if so, how much more?
 

·
Super Moderator
Joined
·
3,649 Posts
I did not say K&N was the best filter, I tried to make out a point with the stock filter.

If changing anything is so bad, why do you not just tell all users to never start, or use their bikes...?
Or worse, getting close to the bike with a tool in hand?
dude, you are heading for a banning - tone it down
 

·
Premium Member
On 2 wheels: 1998 - Rebel 250, 1980 - CB125, 1982 - CM125, 1980 - CM200, 1987 - Yamaha FZ750
Joined
·
17 Posts
OK, but that goes for your co-moderator too.
Before I leave this, I just want to say; I really believed this to be a forum for hobbyist & users, this part marked under "Knuckle Busting | Repair | Modifications & Gear"
And, (for me), any hobby-object's cost is of no elses business. If I ask here how to fit 6 carbs + turbo to my Rebel, I expect to get a better answer than ; "what a waste of time and money, get a bigger bike".
I know, as most other members here, that we have options. That is not why we ask HERE.
If someone searches for <performance>...the same answer comes up, again and again. "No-no. Cannot be done."
If I want to stick with my Rebel, and wring out 80 horses, or "die" trying...I's up to me.
I know it cannot be done, within the factory block & cylinders. But I also know diy-ers capable of doing it, even casting a new aluminium-block in the garage.
Or maybe make the twin into a triple.
Nothing is impossible. It just cost more...and probably takes longer...
 

·
Super Moderator
Joined
·
3,649 Posts
OK, but that goes for your co-moderator too.
Before I leave this, I just want to say; I really believed this to be a forum for hobbyist & users, this part marked under "Knuckle Busting | Repair | Modifications & Gear"
And, (for me), any hobby-object's cost is of no elses business. If I ask here how to fit 6 carbs + turbo to my Rebel, I expect to get a better answer than ; "what a waste of time and money, get a bigger bike".
I know, as most other members here, that we have options. That is not why we ask HERE.
If someone searches for <performance>...the same answer comes up, again and again. "No-no. Cannot be done."
If I want to stick with my Rebel, and wring out 80 horses, or "die" trying...I's up to me.
I know it cannot be done, within the factory block & cylinders. But I also know diy-ers capable of doing it, even casting a new aluminium-block in the garage.
Or maybe make the twin into a triple.
Nothing is impossible. It just cost more...and probably takes longer...
The type of hobbyist who can cast a new block in the garage would not be asking those types of questions here. Maybe 1% of the performance question askers actually try to do something, so the correct response is "get a bigger bike". Of course, if you do start a 80 hp Rebel project we would all be interested in your difficulties and decisions, progress pics, the whole 9 yards. Don't let us discourage you.
 

·
Premium Member
On 2 wheels: 1998 - Rebel 250, 1980 - CB125, 1982 - CM125, 1980 - CM200, 1987 - Yamaha FZ750
Joined
·
17 Posts
What can be done... if you dare..:
 

·
Registered
Joined
·
358 Posts
I do not understand the "resistance" against dual-carbs. And most among those that never tried it.
Also the negative tones that exist here, when tuning is mentioned/asked for.
Cobra2 - Just in case you were referring to me, let me clarify. I don't write very well. I think I come off negative to most who may read my posts. But I'm pro-modification. It is fun. And personally, I think a whole Rebel 250 engine is cheap enough, that I agree with you. Who cares if you blow it up, go get another one. I'd rather not blow it up though.

But my point was that, if people who want to go to dual carbs for more power, the carb alone (single carb, dual carb, different carb maker) is not the answer (in my opinion). Because the stock carb can just plain gitter done. It can deliver ****tons of fuel (for this engine), and it can run lean for serious mpg … all on 1 setup. That's not an opinion. I have an AEM 0300 AFR gauge running on my Rebel.

But, something I'm not familiar with, if changing the intake on a dual carb set up results in using an intake that has better flow than the stock one, that would result in more power assuming the setup was tuned well. And it would be fun to achieve. But keep in mind, even if it results in 40% more power, which is a huge percent and maybe not realistic, 40% is an additional 6 or 7 horsepower. I enjoy mods as well as anyone, but getting much out of this engine … well, a person may want to keep their expectations in perspective.

A 4 valve head, fuel injection and boost would be SO MUCH FUN on a 250 Rebel.
 

·
Registered
Joined
·
358 Posts
What can be done... if you dare..:
I don't get what that video is supposed to demonstrate … what is achieved? Sound? Not mounted in a frame? Am I missing something?
 

·
Super Moderator
Joined
·
29,293 Posts
Cobra2 - Just in case you were referring to me, let me clarify. I don't write very well. I think I come off negative to most who may read my posts. But I'm pro-modification. It is fun. And personally, I think a whole Rebel 250 engine is cheap enough, that I agree with you. Who cares if you blow it up, go get another one. I'd rather not blow it up though.

But my point was that, if people who want to go to dual carbs for more power, the carb alone (single carb, dual carb, different carb maker) is not the answer (in my opinion). Because the stock carb can just plain gitter done. It can deliver ****tons of fuel (for this engine), and it can run lean for serious mpg … all on 1 setup. That's not an opinion. I have an AEM 0300 AFR gauge running on my Rebel.

But, something I'm not familiar with, if changing the intake on a dual carb set up results in using an intake that has better flow than the stock one, that would result in more power assuming the setup was tuned well. And it would be fun to achieve. But keep in mind, even if it results in 40% more power, which is a huge percent and maybe not realistic, 40% is an additional 6 or 7 horsepower. I enjoy mods as well as anyone, but getting much out of this engine … well, a person may want to keep their expectations in perspective.

A 4 valve head, fuel injection and boost would be SO MUCH FUN on a 250 Rebel.
I think you express yourself just fine, and I don't think your posts are negative.

I don't get what that video is supposed to demonstrate … what is achieved? Sound? Not mounted in a frame? Am I missing something?
What can be done... if you dare..:
I'm like 7milesout, I don't see what point the video is trying to make.
 

·
Registered
Joined
·
358 Posts
A 4 valve head, fuel injection and boost would be SO MUCH FUN on a 250 Rebel.
Thinking back on that statement, a 4 valve head would likely be very complex and or costly to convert to on a Rebel, and therefore not worth it for most. However, with enough boost, extra valves are less valuable. So maybe just fuel injection and boost. However, changing from the stock carb to a fuel injector or two, would simplify boost issues associated with the stock carb.

I've never messed with the programming involved with fuel injection. I would love to be as fluent with fuel injection as I am with carburetors. I would imagine I would mainly just need to have software and learn said software. I need to take Fuel Injection Programming 101. That would be fun … if I only didn't have to go to work too.

In my opinion, the main problem I face is, the mods I do that have some kind of benefit, I would like to make them accessible to all … "it ain't no fun, if the homies can't have some." And the amount of money spent on a foolproof, easy to install "boost and F.I. kit" would be very high, for what … 7 to 10 horsepower? I would assume boosting a 17 hp engine to 40 horsepower will yield, many problems. To stay away from problems, I can't imagine adding more than about 10 horsepower to a 17 horsepower engine. And who's gonna want to spend $1,000+ for 10 friggin horsepower? Not many me thinks. In my mind, it wouldn't be fun to develop a "kit" that nobody would want.

So my mind has sort of retired to just enjoying my Rebel in stock form as much as possible. I'm still going to optimize the carburetion, but will likely leave it at that.
 

·
Registered
Joined
·
65 Posts
OK, but that goes for your co-moderator too.
Before I leave this, I just want to say; I really believed this to be a forum for hobbyist & users, this part marked under "Knuckle Busting | Repair | Modifications & Gear"
And, (for me), any hobby-object's cost is of no elses business. If I ask here how to fit 6 carbs + turbo to my Rebel, I expect to get a better answer than ; "what a waste of time and money, get a bigger bike".
I know, as most other members here, that we have options. That is not why we ask HERE.
If someone searches for <performance>...the same answer comes up, again and again. "No-no. Cannot be done."
If I want to stick with my Rebel, and wring out 80 horses, or "die" trying...I's up to me.
I know it cannot be done, within the factory block & cylinders. But I also know diy-ers capable of doing it, even casting a new aluminium-block in the garage.
Or maybe make the twin into a triple.
Nothing is impossible. It just cost more...and probably takes longer...
I'd tou want a Rebel to triple the horsepower maybe you should look at the 2017 and up.its not smart to spend more on trying to get a 250 to do more than it's made to do, but since it seems you are more intelligent than the Honda engineers, go for it.
 
21 - 40 of 41 Posts
Top