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All better now.
I like to leave the raw finish from the cutter but if you think you need to smooth it out have at it.
I am sorry but I thought I had a before photo of the exhaust port but was mistaken. The issue was it had an hourglass shape to it and was very irregular. I removed the most material midway just past the bridge. You can open it up a little just be careful not to go bigger than the gasket. I will throw some jetting specs down for pump gas when possible. The bike has a cracked frame/foot peg so its likely to be a while.
You might want to check out Eric Gorr's porting tips for that bike -
https://www.eric-gorr.com/files/pdfs/model_tuning_tips_honda_cr.pdf
The Shop
Thanks Bro but the guy that rides it is 270# so that's about as far as I am going to take this one.
To take advantage of the larger ,smoother boyesen ports the cases can be altered to remove the flow restriction across the transfer tunnels. If you put the cylinder back on the cases without a piston in and reed block in you can see the area that can be changed.
The proof is in the pudding.
This is the area Dog was alluding to. Using the gasket as a template the photo shows the restriction. I could not photo the actual amount of restriction but it was quite significant. That being said the way the stock ports look doing this without fixing the ports minimal gains would be indicated. Be sure and mask the area thoroughly as to avoid any metal ingestion into the bottom end.
The rear transfers need to be matched up as they are have uneven chordal width.
Good call JBone. The mismatch appears to be about 3mm. I flowed them and the left side was reduced by 30%+.
I still got it man, I still got it 🤣
That pictured reminded me of what I found with my CRE500.
* CRE500s here in OZ were a batch of CR500s that Honda Australia got set up for ADRs in 2002 - Australian Design Regulations - to have as a registerable ('plateable' to Americans, I think you'd regard it as) big trail bike to fill in before the 450Xs came out. Lights, Blinkers (HM ignition) , the whole shebang. One of the craziest ideas from a distributor there has ever been. I bought one because I got it at dealer price, and it was going to be little more than a display bike. It has since been used now for over 20 years, continually, while other bikes have been and gone. It's my 'Keeper' bike. *
I did a couple of run in rides, then decided to 'frame it' as I tend to do with a new bike. The CRE500s were really a Friday Arvo / Parts Bin Build bike.
Well, The left hand 'Boyesen Port' was almost completely closed off, with a near 15mm ball of alloy casting blocking it off. The RH one not much better. Transfers in the cylinder, were not much better. That, combined with the ADR muffler, with it's 16mm ID final core, made for a rather strange engine. Mind you, to pass ADRs, the bikes also had one Reed Valve replaced with a steel, solid plate, a Slide restrictor that only allowed about 12mm of slide lift, and a washer welded into the head pipe with around a 20mm hole in it. It was never ridden like that, by the way.
I rectified that, and matched the cases and barrel, and did some light porting mods I'd done on previous CR500s I'd had, just to make the bike smoother throughout it's range. As I always say, it's a Big Cuddly Teddy Bear of a Bike, that you just need to be respectful of.
Sounds more like a Kodiak. I am going with it's the bike in your avatar.Very cool, thanks for sharing.
Not exactly what I would call easy porting but it is what it is. This part takes a steady hand and experience helps. After performing the JBone transfer mod I re-flowed the jug to my satisfaction to ensure balanced flow.
Things are looking very promising...
270lb rider? Add a billet clutch basket now. I exploded the stock one on my CR85 when I was a kid during the first race after porting the cylinder.
I ran into an issue with the VF4R reed stops being compressed significantly by the roof and floor of the intake so more work was needed. I clearanced it and made some final adjustments to the boost ports. The VF reed block needed matching to the intake manifold/carb boot just has every VF reed cage I have ever installed. Jetting specs will be forthcoming.
I know it has been a bit but I wanted to update this. The end result is nothing short of amazing. The bike pulls hard off the bottom into a strong midrange that builds quickly into a solid hit. That flows seamlessly into a top end where I never found the end. It will wind for days but just trail riding it never signed off. It just keeps pulling but I short shifted with the front clawing for air in every gear.
Ended up with 38 pilot, 125 main, 24NAAJ needle in the middle. Running non-eth 90 and bely ray si7 40:1. Runs nice and crisp/clean.
Vforce 4R, FMF Fatty.
Looks and sounds like a hoot to ride!
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