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Old 10-30-2011, 02:17 PM   #61
cyclewizard
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Originally Posted by Lane_N View Post
Thanks for the detailed response, This stuff is great reading.

Now, are you currently making a piston that sets the deck clearance where it belongs for the 100-102mm bore? If you aren't cutting that flavor, is there a readily available off the shelf alternative that would work?
If you want an off the self piston than the 10.5.1 JE 100mm 101mm or 102mm is what you will need.
Make sure it's for the XRL and not the XR600R motor they are different

I can sell you them at my dealers cost to help the ADV riders out here.
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Old 10-30-2011, 02:26 PM   #62
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Originally Posted by Wattner View Post
CW, can you discuss some of the idiosyncrasies of carburetors, tuning and your experiences with different carbs?

I remember back in the day of the "New" XR650L and the Honda boys sourcing the CV carbs for the big breather motors for desert work on the kickstart RFVC bikes. If I remember correctly, they took the CV carb, bored them, reworked the diaphragm and a few other internals and had them working pretty good. I used the Mikuni Flatslide at the time with great results... Now with the Dave's mods and pumper carbs, what is the hottest set-up, or once again benefits of each carburetor that you have used.

I know we have spoken about the Mikuni 42 pumper and have several of them now. The good thing about the Mikuni is there are only 3 circuits and jetting is easier than the KeiHin, especially on stock or close to stock motors.

The Keihin is more complicated and has more circuits, so it can be dialed to tighter tolerances, but you have to REALLY know all of the circuits inside and out and the symbiotic relationship of a small tweak in one circuit and it's effects on another.

Admittedly, one of my weak-spots is jetting. I have no problem with the old Flatslide, a stock CV and a Mikuni, but the KeiHin is beyond what I WANT to mess with. I like to ride and wrenching is ok, but I simply get frustrated tearing the carb out multiple times for little tweaks, so I end up with just riding when I get close and am missing some performance with the KeiHin.

I have several of the Mikunis now and want to try the KeiHin (since CW will do the tuning...) I have sold one of them (used..) to Garry (CW is beginning a build on his "L" now) and still have another new Mikuni 42 pumper carb with many jets and cables that I would like to get rid of if anyone is wanting a friendly to tune, so to speak pumper carb. PM if anyone is interested.

In the end, we will have a CV, Mikuni Flatslide, Mikuni Pumper and KeiHin to play with on the different motor configutrations.

I know each motor configuration and exhaust all play into the mix, please share some info when you have the time, and if you don't mind ;-)
Sure can, I have dynoed all the carbs plus the eddy, let me find the info and I will post a reply.
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Old 10-30-2011, 05:22 PM   #63
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Originally Posted by cyclewizard View Post
Sure can, I have dynoed all the carbs plus the eddy, let me find the info and I will post a reply.

Finally a thread I can relate to... What is your opinion on the old big port twin carb motors???


I would like to discuss engines with you. Great info, now how about bore to stroke ratio???

IMO the 100mm x 75mm XL600R has the best bore to stroke and rod ratios of the big RFVC engines.

BTW can you build a long rod XR650L 105mm big bore engine?


Thanks

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Old 10-30-2011, 05:56 PM   #64
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This is a great thread, subscribed!!
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Old 10-31-2011, 05:14 AM   #65
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Originally Posted by MetalGuru View Post
Finally a thread I can relate to... What is your opinion on the old big port twin carb motors???


I would like to discuss engines with you. Great info, now how about bore to stroke ratio???

IMO the 100mm x 75mm XL600R has the best bore to stroke and rod ratios of the big RFVC engines.

BTW can you build a long rod XR650L 105mm big bore engine?


Thanks
We ran the twin carb big port motors back in the 80's and 90's on our flat track bikes, they are by far the better motors with there Rod Ratios and twin carb heads.

I build a longer rod to change the poor rod ratio on the XRL motor to address this problem, but in order to do this you have to use one of my pistons or use the oem piston with it's higher pin height.
The OE piston sits in the hole roughly .100 to .110 so I build a rod that's longer and will give you more comp, I started making them when wiseco had there comp #'s off on there XRL line of pistons to raise the compression and give better rod ratio's...

But there's one catch, I wanted to beef up the big end pin because I didn't like the small 36 mm one that the manufacture "Honda" went with. I use a 37mm pin so you have to mill the pin hole to except it.
It's not a big deal for me but for the DIY crowd that has no access to machinery it could be to complicated for them.

The XR600r comes with a 38 mm big end pin, the reason I went with the 37 mm pin is for extra strength and it still leaves room for crank stroking.

It's a real beefy rod, customers have ran Nitrous and a Turbo with it and it holds up.
I like to keep my R/R's in the 1.75 to 2.00 range for less cylinder side loading.
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Old 10-31-2011, 05:24 AM   #66
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I'm building a long rod 10.5.1 724cc motor for katbeanz right now, they work real good with just the CVcarb and and aftermarket pipe or just a plain ole slipon. that's the beauty of it.
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Old 10-31-2011, 04:47 PM   #67
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Quote:
Originally Posted by Wattner View Post

discovered a melting Hotcam. This was my motor that melted down a couple of years ago and was sent to XR's only for a rebuild.


I apologize in advance that I got hopes up for an HRC cam and now cannot deliver the specs, as it appears I have been ripped off.

Update to follow.

So C-DUB does this mean that the 628 cam that you were going to get the spec's from is now just another melted Hot Cam (like there aren't enough of them around) and you don't have a true HRC 628 cam to copy from?

Kinda like that supposed 628 cam I bought last week on e-bay.

No soup for us 628's wanna be's???

Say it ain't so, Say it ain't so C-DUB
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Old 10-31-2011, 07:35 PM   #68
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Quote:
Originally Posted by cyclewizard View Post
I'm building a long rod 10.5.1 724cc motor for katbeanz right now, they work real good with just the CVcarb and and aftermarket pipe or just a plain ole slipon. that's the beauty of it.
Think it needs a big fin head? Modded oil pump is working real nice, your jetting specs and ported head too. :swoon

Just home from ripping around Arkansas. I'll get your tank on the way this week.
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Old 10-31-2011, 07:54 PM   #69
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So what are your thoughts about how a twin carb XL head would work on a 724 motor?

I think the dual carb head and carb setup is the best design Honda built.

What are your thoughts about this?

I don't know about the combustion chamber differences...

I have never had a pumper carb to compare the response to, but I can't see it being that much better. The dual carbs will win on fuel economy I'm sure.

The carbs I have are 28mm oval bore carbs. The primary carb is 28mm x 31mm and has a 28mm x 33mm secondary carb.

The heads intake ports have the smaller primary port with a larger secondary port. Both exhaust ports are huge when compared to an L single carb head. I'm sure you know this, I just want to be on the same page.

I wonder if running a different cam lift/duration for each intake along with proper porting of each port and a oversized secondary intake valve would work along with oversized exhaust valves and a big exhaust cam.

Just a thought I have had....


Your thoughts would be great.

Btw, I've enjoyed how you are describing the principles of operation and engine design principles are very well written. So far your thoughts about engine design are the same as mine.

I'm a ex-master tech of 20 years and have built many circle track and drag motors. I quit wrenching due to my back. Its great to find a thread like this. I would like to set-up a fuel injection system on another XR at some point. I kinda enjoy mapping and tuning fuel injection.


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Old 10-31-2011, 08:21 PM   #70
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Shock

How many of you know that the shock is off set on the single carb XRL as compared to the dual carb XR600r ???
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Old 10-31-2011, 08:33 PM   #71
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Cyclewizard, you're Kevin Cameron's little brother who drinks beer.
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Old 11-01-2011, 04:02 AM   #72
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Originally Posted by katbeanz View Post
Think it needs a big fin head? Modded oil pump is working real nice, your jetting specs and ported head too. :swoon

Just home from ripping around Arkansas. I'll get your tank on the way this week.
Lets do a big finned head, I'm glad the modded oil pump I sent you is working good..and yeah we have to port the head to make her inhale and exhale..
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Old 11-01-2011, 04:03 AM   #73
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Cyclewizard, you're Kevin Cameron's little brother who drinks beer.

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Old 11-01-2011, 04:17 AM   #74
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So C-DUB does this mean that the 628 cam that you were going to get the spec's from is now just another melted Hot Cam (like there aren't enough of them around) and you don't have a true HRC 628 cam to copy from?

Kinda like that supposed 628 cam I bought last week on e-bay.

No soup for us 628's wanna be's???

Say it ain't so, Say it ain't so C-DUB
we lucked out, I actually found the specs, I had them logged into my computer and forgot I had them...
So they are still available if you want one..

When I checked Mikes cam something was fishy with the specs they didn't seem right"weak" so I checked a hotcam I had laying here and sure as shit they were the same..I feel bad for Mike, I'll grind him a HRC cam and throw the hotcam in the scrap pile. his cam was galled and so was his rockers.
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Old 11-01-2011, 04:32 AM   #75
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Originally Posted by MetalGuru View Post
So what are your thoughts about how a twin carb XL head would work on a 724 motor?

I think the dual carb head and carb setup is the best design Honda built.

What are your thoughts about this?

I don't know about the combustion chamber differences...

I have never had a pumper carb to compare the response to, but I can't see it being that much better. The dual carbs will win on fuel economy I'm sure.

The carbs I have are 28mm oval bore carbs. The primary carb is 28mm x 31mm and has a 28mm x 33mm secondary carb.

The heads intake ports have the smaller primary port with a larger secondary port. Both exhaust ports are huge when compared to an L single carb head. I'm sure you know this, I just want to be on the same page.

I wonder if running a different cam lift/duration for each intake along with proper porting of each port and a oversized secondary intake valve would work along with oversized exhaust valves and a big exhaust cam.

Just a thought I have had....


Your thoughts would be great.

Btw, I've enjoyed how you are describing the principles of operation and engine design principles are very well written. So far your thoughts about engine design are the same as mine.

I'm a ex-master tech of 20 years and have built many circle track and drag motors. I quit wrenching due to my back. Its great to find a thread like this. I would like to set-up a fuel injection system on another XR at some point. I kinda enjoy mapping and tuning fuel injection.


The XL600 twin carb head is highly sought after in the flat track world for it's great pull out of the corners and high speeds down the staights.
The idea behind having one port larger that the other is to create swirl in the mixture for a better burn and throttle response so you want to keep the ports the way they are if your going to do any porting on the head, one larger than the other.
For the carbs, you don't need a pumper carb on that motor the twin round slides work great, I had a 83XL600R that was stock but with taller gearing and it would do 105 to 108 mph depending on head winds.

It's by far the best of the lot if you can find them, I have a few here that I was thinking about doing a 106mm kit on them.
I think it would be a terror with 10.5 or 11.1 comp an HRC cam grind "now that I found the specs" and keep the stock header because they already have larger tubes than a XRL has and just add a slipon.
You could build one of these on the cheap and have one sweet power band, Yikes.....

here's a pic that Wattner sent me of a xl600 motor..it has a pumper carb on the one side.
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