Topic: Engine upgrades?

[napoleonb]

Absolutely no reason for that grub screw. The shoulder on the shaft goes against the inside of the clutch cover and prevents any movement.

You're right, its more for piece of mind than anything else.

[simon#42]

yes i would use a grub screw as well .

[Tracksnblades1]

To my understanding the more modern factory Honda CR dirt bikes also use aluminium clutch plates.
This makes sense since every 60 hours or so you have to replace a lot of components anyways so excessive wear and debris from the plates woudn't make that much of a difference.

7.5 hours is the transmission oil change interval in Honda CR Service manuals. When riding well below-competitive levels and using Honda's recommended HP oil with aluminum clutch plates in the CR's, the oil turns black and has aluminum contamination in under the 7.5 hour interval. I used Case/IH HYTRANS oil in our 01 Cr500 (steel plates) and never experienced it turning black or metallic skimming in the drain pan. Some on the  CR500riders forum promote using the advanced power shift/hydraulic oils in them.

I personally believe at very competitive levels, the aluminum plate is an "Old Smokey Yunick" thing. "If you don't, someone else will, and you'll loose".

[slikwilli420]

yes i would use a grub screw as well .

But where is the shaft going to go? It cant go too far inside and the clutch cover keeps it from moving to the outside. There was no screw when the kick start clutch was in there and that has been replaced by a spacer.

[napoleonb]

The kickstarter shaft is being fed a little oil from the final driven shaft bearing closest to it and this is being gravity fed to the gear by a hole in the shaft.
If the shaft rotates (rotation is normally countered by the spring and stopped by the flange) this hole might face upward and limiting the supply to the gear.
No risk of the shaft escaping and if the friction keeps it in place no problems there as well.
But when installing it can rotate without me noticing.

[bwaller]

Curious about the Case/IH transmission oil and your wet clutch? Must have been fine.


 I used Case/IH HYTRANS oil in our 01 Cr500 (steel plates) and never experienced it turning black or metallic skimming in the drain pan. Some on the  CR500riders forum promote using the advanced power shift/hydraulic oils in them.

[Tracksnblades1]

Curious about the Case/IH transmission oil and your wet clutch? Must have been fine.


 I used Case/IH HYTRANS oil in our 01 Cr500 (steel plates) and never experienced it turning black or metallic skimming in the drain pan. Some on the  CR500riders forum promote using the advanced power shift/hydraulic oils in them.

BW,
The HyTrans works very well in the two stroke transmission, very smooth shifting and little or no clutch fade. I think John Deere TransGuard would work as well.  I've tried HyTrans in the aluminum clutch plate Cr250s/125s we have as well. The aluminum clutch plates contaminate the oil quickly. The drained oil in pan looks like a layer of never seize is floating on top. I couldn't imagine a four stroke oil filter not plugging at competitive level riding. The Honda 4 Stroke CrFs have very short 5hr  engine oil change intervals, I'm thinking. At my level of riding Dirt or Street aluminum plates are not a major performance concern of mine.

The CaseIh HyTrans as you probably already know is designed for powershift "wet clutch" transmissions, hypoid rearend gears, plantetarys, needle bearings, needle thrusts etc as well as Hydraulics systems, hydraulic motors etc.
The older non-cvt trans typically use multiple wet clutch speeds and range gears that are shifted without clutching. The formulation doesn't have to include the requirements of the internal combustion engines
The HyTrans and  TransGaurd brands are not known to attack brass. Beware some trans/hydraulic oils will.
Don't ask me why I know Caterpillar TO30 will dissolve brass. Some hydraulic charge pumps have brass separator plates.
👍

[simon#42]

yes i would use a grub screw as well .

But where is the shaft going to go? It cant go too far inside and the clutch cover keeps it from moving to the outside. There was no screw when the kick start clutch was in there and that has been replaced by a spacer.

to stop the shaft from rotating

[MRieck]

The aluminum plates I have used have been cyro treated and hard anodized

[Tracksnblades1]

The aluminum plates I have used have been cyro treated and hard anodized

Sounds like the best of both worlds.
Fiction coefficient near that of steel, and weight and thermal conductivity of aluminum.
Perhaps a Barnett offering..?

[napoleonb]

Yet another question while I'm still tearing down engine parts.
How about stepped studs for the cam towers, these are the same as the 4 M6x56 bolt studs only with M8 in the bottom instead of M6.
Although there are slightly less threads in the material because of the different pitch there should be more surface area which doesn't strip the studs out that easily.

https://www.belmetric.com/metric-step-studs-6810mm-c-9_73/s6x8x56blk-step-stud-black-p-11939.html

Did anybody try this mod?

[MessnerMoto]

Yet another question while I'm still tearing down engine parts.
How about stepped studs for the cam towers, these are the same as the 4 M6x56 bolt studs only with M8 in the bottom instead of M6.
Although there are slightly less threads in the material because of the different pitch there should be more surface area which doesn't strip the studs out that easily.

https://www.belmetric.com/metric-step-studs-6810mm-c-9_73/s6x8x56blk-step-stud-black-p-11939.html

Did anybody try this mod?

I made those from used cylinder studs ... cut them and threaded to M6... In my engine currently.....

[napoleonb]

Currently i'm looking at the cylinder heads, I've got a F2 and K2/K6 with matching barrels.
I will keep it 750cc but want to use the original CR31's and a K6 crankcases.
I'm aware that there are some problems combining K and F parts in regard to the oil flow.

The F head already has 31mm inlet channels and bigger valves whereas the K head only has 29mm but higher compression.
Which head do you guys recommend to start with?

[Old Scrambler]

Piston choice may be different for K vs F2 because of larger/deeper chamber and 1mm shorter valves. Limited decking due to larger valve at edge of bore.

[napoleonb]

Depending on which head I'm going to use i will choose pistons and or decking the head.
The oil return is solvable IMO but which head to use as the base is what I'm still struggling with.

[bear]

In my opinion you would be better served using a 300 casting rather than a 410 for the application you are describing.
A pm to MRieck might be worth while.

(A Caveat) 
I'm only a broken down ex racer with no engineering credentials whatsoever. 

Cheers
Brian

[bwaller]

At some point Bear we all fall into the “broken down racer category”. It’s how the experience is shared, and then accepted by others that tells the tale. In your case there is nothing broken about what you bring forward. Except maybe that pile of parts out back!

 

My thought is keep the compression up with as flat a piston dome as possible, so smaller chamber with the largest intake valve possible. Depending on displacement reduce the exhaust valve in favour of the intake. A smaller dome will require less ignition lead, which is more efficient. Find the best way to build squish which also helps efficiency. PeWe showed pics of his chambers that had a shelf machined to accommodate larger bore. Concentrate on chambers, then take a mould and let the piston manufacturer design a dome to offer the CR you desire. Those days are gone when we had to settle on some old piston design.

[napoleonb]

I think I will go with the K head, eliminating the oil flow adaption between F and K parts saves time as well.
As I wont be going racing with this engine in the near future pushing the limits isn't really sensible money-wise. That being said I would like it to go fast within a safe zone for reliability.
Reworking the head and flowing it to make the most of the camshaft/valve/carb/piston combo is inevitable.

Because of the "proper" CR750 look I would like to make the most out of my original keihin carbs.
I assume I could rework the inlet mounts to make the F parts with the 31mm inner diameter fit the K head and carbs. Not sure if the thread for both is the same but I will try to remove them form both heads and compare those. If its the same I will just swap the parts, if not I will rework the head or inlet mount to fit whichever is easiest.
Enlarging the inlet valve and decreasing the exhaust valve seems to me like a good start.

I will start to tear down the head and figure a way to make the inlet mounts fit the carb and boots.
Which boots do you guys prefer for the 31mm keihin smootbores?

[MRieck]

I think I will go with the K head, eliminating the oil flow adaption between F and K parts saves time as well.
As I wont be going racing with this engine in the near future pushing the limits isn't really sensible money-wise. That being said I would like it to go fast within a safe zone for reliability.
Reworking the head and flowing it to make the most of the camshaft/valve/carb/piston combo is inevitable.

Because of the "proper" CR750 look I would like to make the most out of my original keihin carbs.
I assume I could rework the inlet mounts to make the F parts with the 31mm inner diameter fit the K head and carbs. Not sure if the thread for both is the same but I will try to remove them form both heads and compare those. If its the same I will just swap the parts, if not I will rework the head or inlet mount to fit whichever is easiest.
Enlarging the inlet valve and decreasing the exhaust valve seems to me like a good start.

I will start to tear down the head and figure a way to make the inlet mounts fit the carb and boots.
Which boots do you guys prefer for the 31mm keihin smootbores?

You will need to replace the exhaust seats if you want to go down to a 27mm valve.

[napoleonb]

Thanks for joining in MRieck.
Do you recommend doing this, or would you just enlarge the inlet valve and keep the exhaust valve the same.
Given the amount of profit gained in doing so is it worth the hassle?

[MRieck]

Thanks for joining in MRieck.
Do you recommend doing this, or would you just enlarge the inlet valve and keep the exhaust valve the same.
Given the amount of profit gained in doing so is it worth the hassle?

Just use the 33.5mm OS intake valves. Bore the seat to 90% of the OS valve OD. You will pick up good CFM

[napoleonb]

Now I've decided on which head and barrels to use I can start with getting rid of the excess parts to fund the porting job
Currently finishing the kickstarter mods, then off to reassembling the clutch cush drive with fresh rubber and lightening the clutch basket.
When all these things are done I will focus on the crankshaft and top assembly.

[gschuld]

I’m particularly interested in your efforts on lightening the clutch basket.

The below are the ones Brent Hyde lightened.  Granted, they are DOHC baskets for his 180RWHP racer.  He did eventually have one fail(cracks developed at the turns), but he was using a non banded basket as a base.  If you look closely, you can see the cracks.  He went to the outer band version afterward and had no further issues(as far as I know anyway)  Ours have the outer support band OEM(bottom photo) and that’s a bonus.

Good luck with the mods and keep us informed👍

George

[napoleonb]

Which clutch lifter piece would you guys prefer, the one with the extra protruding pin and a bit taller or the flat one which and why?

[napoleonb]

Well I finally had some machining time to spend so I started moderately with an 8% weight saving over stock.
If this works I can go down to 11% before I don't trust it to hold up for longer periods of strain.