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I'm considering that PVL ignition just to have something new and reliable. Although it sounds like there might be some performance increase too. I did find an "E" ignition in Australia that I picked up.
I have a DG pipe, and I have a pipe from Holly on the way too. I prefer the hydroformed look instead of the multiple cone look. So I'll have those pipes to compare to the stocker.
Will be running a 36mm Mikuni carb. Was thinking of sending the carb to Dick's racing for a taper bore 39-39mm, plus their power jet mod which Motocross Action raves about.
The Shop
Back in 78 I was lucky - my 250 used to holeshot almost every time. Even at saddleback against open class bikes. I even let a couple of friends race my bike and they pulled hole shots with it. Bone stock motor - i just got a good one from the factory.
http://www.vintagemx.us/message_board/viewtopic.php?t=7262&highlight=
I reluctantly sold it and the guy who bought it let Micky Kessler race it.
Micky won a ton of races on that bike.
I missed it so badly that I bought another that I am building.
I think the 250's stock have enough power. Just replate the cylinder, use a Mikuni (as you are) and the pipe should be more than enough.
Richard
Richard
I'll give you as much detail as I can. Hopefully, you'll find it interesting (and maybe helpful) and not too boring!
We took a good friend's '79 and and my own 1980. Both are full on, top spec, PDE builds and both have been ported, I did a little more work on the 1980, mainly on the exhaust port. I didn't change any port heights / timing, but really opened up the boost ports and transfers. I really like the 1980 power delivery so I didnt want to change it.
Both bike have Nikasil bores, Wiseco pistons, Pro-form pipes, 38mm Kehin flat slide carbs and stock ignition systems and to start with, stock ignition timing.
The stock ignition is very, very reliable and from my experience, I wouldn't change it. We do swap the coils to a later OEM Honda one, (This requires a 5 minute soldering job to extend the wires and to put the correct connectors on). The old coils are really the only "weak" area in the system.. they are 30yrs old!! VERY occasionally a CDI can fail, but that is very rare. The grade of the system is actually not important, so long as they are all matching components, IE rotor, stator coils and CDI of the same grade. They are graded so that the manufacturing tolerances can be wider. They then just matched components to give the optimum performance for the whole system. One grade is no better than any of the others (despite the "legend" of the E grade being superior).
If the rules of your racing organisation allow a flat slide carb, then the 38mm Keihin from the later CR's (86-96) is the BEST carb to fit. All the parts are still available and easy to get. Jetting it is really easy, cables and throttle assy are also really easy to sort (we use '97 CR throttle assy, or a Domino copy and an OEM '97 cable) and it can be slotted straight in. We do make a little mod to the inlet stub: - we machine an extra groove so it seals a little better in the inlet rubber but I know of people who don't do this and it works fine..... it's just not as easy to pop in when fitting.
Pro-form pipes seem to work well but are not very well finished and fit like crap. We often have to cut and re-position brackets to get them to fit!! We'll probably be swapping to Holly's pipes for next season, I was talking to him yesterday and 1980 pipes should be ready to go towards the end of the year. We have tried Jemco pipes but we really didn't like the power delivery. It made the 1980 almost un-rideable as it's power delivery was so "explosive". Also, the fit was very strange, with a massive gap between the vertical cone and the frame tube. You could, literally, get your foot caught in it! However, they are well finished and bolt straight on.
What did we find on the dyno?...
In 1978/79 Honda, quoted the power output as 36PS at the crank. The Fox set up guide from the same era quotes 27 BHP at the back wheel. As you probably know, NO manufacturer takes a stock bike straight off the line to do their tests. The motors will be blue printed and tweaked and then the figure quoted will be on the "generous" side. Obviously, every Dyno will give slightly different figures, so its best to use them as guide only.
The 1979 produced 26.5 BHP at the back wheel. Almost, exactly what the Fox guide said it did "back in the day" but we were dissapointed considering the work done to it.
The 1980 was a brand new motor, it had been fired up once and run for only 5 minutes or so before its dyno run. It produced 30.6 BHP at the back wheel and 24.4 FT-LBS of torque. We were quite impressed!!
We honestly expected more from the '79, although it did pull a further 1000rpm over the 1980, it's figures were down. So to test out the theory of the E ignitions, we swapped in a complete E system (it had an A system to start with) and ran it again... It actually produced less power!! 24.3 BHP! Very disapointing! The dyno operator was of the opinion that the figures indicated that the ignition was slightly retarded.
So.... we started tweaking! We pulled the dowel out of the stator plate and advanced the ignition by around 0.4mm.(I can't quite remember the exact amount) This gave a 2 BHP improvement up to 26.4 BHP... better, but not enough! We then backed the igniton off to around 0.2mm advanced over stock and tried again. Instantly we had 30.3BHP, 24.4ft-lbs of torque and big grins!
We didn't have time to start tweaking the ignition on the 1980, so who knows what we could have got out of it! Both bikes seemed to be running slightly rich at the top end so since then we've come down a 170 main jet and on the track they both feel cleaner. When we get the new pipes, we'll go back on the dyno and do some more "in depth" testing.
We're also looking at the possiblities of having digital, programable CDI units made for them . This would give us the ability to get the optimum ignition settings through out the entire rev range for each individual motor. It's quite common in road racing and we can see distinct advantages!
What the DYNO did show, clearly, was the difference in the power delivery of the 2 bikes. The '79 came on to the pipe with a bang and had an extra 1000 RPM over rev compared with the '80, although peak power was at virtually the same RPM. The 1980's power curve was visibly much smoother and came in a little lower down in the rev range, which confirms the riding experience!
I rode the '79 at Farleigh Castle a couple of weeks ago. The main difference that I found between it and the 1980 was on part throttle openings. On the my 1980 I can gently roll the throttle on and the power comes in smoothly with no big hit. Doing the same on the '79.. the "hit" was more noticable. It doesn't produce any more power, it just comes in with more of bang but once "singing", I would say there is nothing to choose between them.
Pics of 1980 barrel below. These were taken half way though the porting process, so one side is still stock.
If you've you've got this far without falling asleep, thanks!!
Stevie
What later Honda coil exactly were you using? Do you have a part #, or I guess just a year/model would suffice?. I'm great at soldering/wiring, so changing connectors is no biggie - Do you have a source though to get the proper connector to plug the new coil into the existing system, or do you have to sacrifice an existing '79 stock coil to get the connectors?
You said it's important to have the components match - the stator, cdi, and rotor (flywheel?). I picked up a spare motor from ebay and the stator cover has an "E" on it, so I assume the stator and flywheel are "E"'s. I believe the CDI's are marked too - are there markings on the flywheel to confirm what letter they are? Gonna be tough finding any more "E" CDI's to match up with these.
Like so much of your other things, I'd be VERY interested if you did a digital ignition!!
Also sounds like I might go back to my original idea of having my cylinder ported for a smooth/broad powerband. Let us know what you think of Holly's pipe when you get to run it.
The coil part number is 30500-HN1-003. We can supply new connectors and new rubber covers. Or even a complete, modified coil ready to go. I tend to put new connectors on all the wiring (Along with new heat proof sleeving and shrink wrap) and if the rubbers clean up well, I re-use them. If the original coil is knackered, or in poor condition I just cut the rubber off for future use and bin the coil.
We use new NGK plug caps, The original caps cant be removed from the coils, and to be honest, I wouldn't use them anyway even if they were removable.
Here's a pic of the coil and how I extend the wires.
The rotors (flywheel) are marked on the inner face, there will be a little circle with a letter in it. (1980's have no markings) the CDI's are stamped on one of the mounting flanges. As you said the stator plates are marked (again 1980's have no markings), so long as everything matches the system should be good. Check the wires going into the CDI. They can crank really close to the box where they enter the resin. Occasionally they can be kinked and broken at that point. If they are good, it's quite rare for the CDI to be faulty. We've only ever had one that was faulty and that was on our 480.
Obviously, as time goes on, CDI's and such like will start to fail and / or become more difficult to find. The stator coils are easy to repair or replace so they will never be an issue. Programable CDI's would be a great way to not only keep bikes out on track but improve them as well!
Stevie
had an idea - if you determined that advancing the timing .2mm on the 79's was a universal good mod for all of them, could you take one of the dowels and tun down half of it by .4mm? The unmodified half would fit into the case normally, but the turned down half would let you rotate the stator plate exactly .2mm and have a hard stop to get the position just right.
And by the way - to advance the timing, do you rotate the stator plate clockwise or counter-clockwise?
The dowel is an interesting idea, we'd have to see if tweaking the ignition worked universally on a number of motors, in different levels of build, with different pipes or carb. I suspect it's probably a very specific thing, each motor will be slightly different.
One of the other things I'd really like to try, is have a whole selection of complete ignitions and try every combination of flywheel, stator coil and CDI, just to see what happens... Although, I feel that doing this maybe a little much when dyno time is £50 an hour!
Oh, one more piece of info, both bikes were run on normal "super unleaded" pump fuel (97-99 octane) with Silkolene Comp 2 Plus fully synthetic oil mixed at 40:1 ratio.
Gotta go pack the van now!
Stevie
I am starting the rebuild of my '78 (which I've never ridden) and would like to build up a good running nice handling version. I have Fox Airs and a set of 44mm (?) forks off a later year CR-125, but otherwise it is stock. Looking forward to getting this thing restored.
Your forks are 43mm if off a later model Honda. Fox Forxs were 44mm
The 1978/79 is a kissing cousin to the 1980. Enough changes to make it a better bike (IMHO), but not enough that one could not borrow a great deal of parts to use on any of the three years. Off the top of my head, the frames, cylinders, pipes, tanks were about the only non-interchangable parts. The 1980 head should NEVER be used on a 78/79 as the head stay is so important to keeping your frame in one piece, but you could use a 78/79 head on a 1980 IF you had to. And I hate the look of the 1980 seat on a 78/79, but it is a direct bolt on.
Richard
Pit Row
I like the look of the metal 78/79 tank way better than the 80 plastic. The 80 tank looks like it sits up too high. I've ridden raced an 80 model back in 1980 and remember the torquey power. In 1978 I bought a new Husky 250, instead of the much better (in hind sight) Yamaha or Honda of the same year. Should-a, Could-a eh?
So now it is time to get the '78 I bought a few years ago, up and running.
The 78/79 uses a single front down tube frame with a side exit exhaust port on the cylinder. The 1980 uses a split down tube frame to accommodate a center exhaust port cylinder.
The 1980 is a little different.
It has a twin down tube frame, with a slightly steeper head angle. No side panel mounting tabs (1980 side panels will fit a 78/79), and an extra upper chain roller. The air-box (and its lid) is a little different (to clear the roller), and it's not rubber mounted. It will fit straight into a 78/79 though. The lower chain roller and its bolt are different. Again they will swap, a 78/79 bolt and roller will fit a 1980 and visa-versa.
The seats bases are white, 78/79's are blue/grey (but dimensionally identical) and they have a plastic tank.
The motor has a centre port barrel, the main inlet into the back of the piston is "un-bridged" (you can see it in the above pics of the barrel. We've modified a '79 barrel to 1980 spec but we haven't got round to trying it yet) There is no cylinder head steady. The left hand crank case has extra bracing under the cylinder base flange. 1980 engine numbers start ME03, (78/79's start CR250R)
The forks are slightly different and the swing arm is 1" longer.
Despite the differences. They are pretty much the same bike. SO much is interchangeable. You can even fit the 78/79 alloy tank to the 1980 with little bit of fabrication. Some people drill the frame, but I prefer to modify the tank mountings to fit the frame.
Bultaco, a good cheap "mod" is to fit the 1980 swing arm, (along with the brake arm and rod) It makes them a little more stable. Also, when you fit the 43mm forks, make sure that from the top face of the top clamp to the axle centre is 914mm.
Stevie
If I'm understanding this correctly, I hadn't really paid attention to the 80 barrel, but I'm surprised to hear it has the large unbridged main intake port. The 78 cylinder's had that humongous single hole in the rear, but the 79's were bridged (horizontal between the big and small port segments.
The E ignition mythology got birthed in the Fox handbook, I believe, and maybe the fact that the claimed Tripes 79 RC 250 was running an E ignition.
My 79 cr250 rocket had issues from the start and was also not making good power, may be like the 79 model tested on the dyno above.
On my bike, when the piston was at BDC it was covering the exhaust port by 2 mm, I know this used to happen in the old days with various reasons for some engines being built like this. Or may be using none Honda crank, rod and piston made this happen. However personally I always thought it was wrong.
A quick fix is to place a 1.2mm spacer under the barrel, with a .5mm each side. After the gaskets are squeezed they measure 0.4mm each. Then the barrel top then needs skimming 2mm. I took 1mm off the top on mine and then skimmed the head to get the correct squish at 1.5mm using a .4mm head gasket.
It really flys now. I wounded if anyone else has changed the port timing.?
g rod or use a spacer.?
what is that swing arm on your bike in the above pic.. the one you designed?
mike
It looks cool and it's length really helps with the handling, but to be honest, I don't like it being on there.
We are working on our own design. All the CAD work is done. It's just no one wants to make the billet parts for us. They are border line for the capabilities of our machine so we have been looking for a company to make them for us.
Obviously, we can't just launch in and make a batch of them. We need to have a prototype and test the hell out of it! No one is willing to make the parts at a reasonable price unless we order 10 or 20.... which is just a crazy amount of money and something we don't want to commit to until we have the first one thoroughly tested!!
We are hoping to get a new machine in later this year which will enable us to make them in house though.
The design is based on the RC "coke bottle" style. It will have weld seams down the center line of each "leg". The front fork section, is to be machined from one piece. Each shock mount and axle block will be machined out of one piece as well. The "legs" are 2 halves, an upper and lower, which will be CNC lazer cut and bent. All from 6082 (Euro version of 6061) alloy and they will be heat treated to T6.
I'm REALLY getting frustrated by the time it's all taking, and the fact that I can't do it all in house! But, they will get done!! The arm on my own bike won't take another season, and we have 3 480 twin-shock builds that will be needing them!
Stevie
Stevie
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