I suspected the cam mod will require bigger jets . I just kept my mouth shut so I wouldn´t influyence anybody´s findings .
It would be a really big help if whe can centralize the findings :
Example : I have the 300 cilinder , I neded to go with this size pilot and that size main . My needle is in this position and I went that many turns out on the mixture screw .
Altitude may be another variable .
Please specify if the jets are Kawasaki / Keihin or Dynojet or what they are .
ATM the main concern is the original carb the Keihin CVK 34 .That´s what more than 90% of the bike are using .
Of course , if somebody will have the time and the money to go to a dyno and have the thing done profesionally that will be even better ( that would be the best ) . They will also give you an atmosferic pressure reading .
Then latter , when whe have the results I can edit the original post and put the sizes in there and that ( even if not final , there are allways some bike specific variables ) will be a great help for those of us who want to do the mod and have carburated bikes .

 

Second report:

351 engine, I only did the intake cam.

A few things that stand right out.

The initial Jerk my arms off when I crank the throttle is gone. Roll on power seems to be better only with the air box lid off.

Since I put the TM36-68 slide carb on the throttle "sticks" at Idle under High RPM decelleration. Its the vacuum sucking the slide where it is. Once I twist the throttle and the vacuum is released its not a problem. BUT I have to be careful because it will pop open and make the bike jerk. If I pull the clutch in to let the revs down, the throttle works fine. Since I did moved the cam ahead 10*, that problem disappeared.

I burned a tank of gas at 67 miles. Its usually closer to 90 miles.

Bike is too rich. This could be why it runs better with the lid off the air cleaner.

I rode yesterday and burned up a tank of gas in the twistys. 7,000 rpm riding, using the power the bike has. It was a great ride. Air cleaner lid OFF. LOUD AS HELL. I do not like the noise but the bike ran great. Above 7,000 RPM it begins to sing instead of just a loud popping noise from the intake. I can get up to 10,000 rpm with the lid off, so like I said earlier its too rich.

It feels smoother and I moved the power band.
bike pulls from 3,000 rpm or less. Before It refused to do much below 4,000 rpm. Seems a little peppier at 7,000.

I ride an SF with street tires only on blacktop.

Probably will do the exhaust cam and rejet to get a full feel of the mod. If I don't like it, back to stock. Read back, I said my bike goes like a raped ape before the mod. It did. (does with the lid off)
David

 

I don't know about MONTHS. That's why I was telling you that United States Postal Service delivery to Europe was only about 12 days. I've never had to wait too long for anything I've gotten from ebay from the UK or Ireland. I've also not had any problem shipping to Europe. I've got parts in Portugal, Spain, Latvia, Serbia, Belgium, Finland, the UK, Netherlands, Australia, New Zealand and Canada. I've only had two hold ups in two years and probably about 300 parts. One got held up in Canadian Customs for nearly a month. The other got returned from the UK because I had 25 for the house number instead of 26, returned as "no such address". I also find it usually is only about 8 days, but saying 12 conforms with that of the post office.

The major question would be delivery time from you. If you could mark timing sprockets and have good instruction, you could simply sell the sprockets ready to install and have directions on how to do the compression release for them to have a machine shop press it out and put it back in. A competent machine shop could do the job if given the needed instruction. Otherwise you do the one or two day turn around on doing the whole job. You could have gears marked ahead of time to make things happen fast.

You see, absolutely not everyone has the skill, equipment, time, or interest in doing that sort of work. Especially if it is done for a reasonable price. And as pointed out, there are very VERY few mods that will give a full 25% increase in power. Carbs and exhausts are literally hundreds of dollars. I find it hard to believe the shipping total to ship it to you and back from you would even be $50. As said, sprockets off and packed into a small flat rate box the shipping from anywhere in the U.S. would only be $13.95 to you.

I wonder how many 250 riders would be willing to pay $125-150 to have the cams set up to be bolted in for a 25% gain in power that don't have the mechanical accumen to follow the procedure or would just rather buy the parts properly set up by the guy who developed the set up. That's way cheaper than a new exhaust or carburetor. Makes me wish I had a 250, but I don't. I have the 650... Maybe I should look at the cam timing on it... You think?

 

Question:

I've never seen it posted here, has anyone ever just plain taken the compression release off the cam?

I know both the electric start 650C owner and the kick start 650R owners have done so. They mention it being a bit harder to spin over, but the bikes still start. The problem with the 650s was that the weights weren't well riveted on. I restaked the rivets on mine to snug up the fit. Others have had the weights come off, so they removed them completely.

Can this be done on the 250 and it still spin hard enough to start the engine on the electric start?

I know a kick start can simply be eased over TDC and kicked - I had and still have Yamaha SR500s and have done it quite often - so that's not even a question.

 

Yes, I can do the ACR retiming but I would have to go back and see how far the ACR would have to be moved and in which direction. So far, I've done about 120 ACR mods to the earlier model 250s and 300s to make them easier to kick over.

Ride on
Brewster

 

Hmmm...sounds like a good ACR mod source on this side of the pond. Now Brewster, you aren't really Marcelino in disguise are you? Very creative way to drum up business...LOL!

Now...I'm totally kidding...but I am checking internet source addresses as we speak...LOL!

 

I took the ACR off my XR650L. It's noticeably strained to start, but the engine was tuned well and started right up. If you have to crank it over a lot, your starter can quickly overheat. If you remove the ACR completely, be prepared to put some new brushes in the starter motor once in a while and don't crank it for long at all.

On a side note - I really am surprised by the number of people responding to this saying "I'm doing this", but have no idea how to tune a carb. People please give the guy a break - learning how to tune a carb is step #1. Don't ask him for jetting advice. If you don't know how to tell lean from rich, read some carb tuning articles.

 

ACR is exactly the same from 90-something till today , the early ones allowed more compresion , then it was retarded , I think you are all to familiar with this .
It´s the reverse of the mod you have been doing . It does not increase the compresion at start , it just restores it to the way it was before rotating the cam . Mine is rotated 2-3 mm more to allow more compresion , but that is my personal choice and another story .
When it´s all said and done , with the engine at TDC that cutter blade that I used to indicate the position ( see the original post ) should indicate the empty space between the round piece and the one below ( the counterweight ) .

 

Checking internet source ? ... Damn ! ...
Brewster is a smart guy who demonstrated a long time ago that he is capable of thinking outside the box !
You should be gratefull that he is on your side of the pond .

 

Using Marcelino's figures, if you retard the exhaust cam, the early 250's and pre-2002 300s will have the added benefit of getting the ACR near the "easy kick" position (if it hasn't already had the original ACR mod done).

Ride on
Brewster