sealing new reeds

[grayson]

Hi, having trouble getting my ccm race reeds to seal. Ive lapped the reed block and oiled the reeds, they looked good last night, but today only a few of them are sealling fully. I can see light through the others. Have not applied much pressure to the at all, just above finger tight- they are socket head screes
Is there something im missing?

[zul8tr]

If you mean they are slightly raised above the reed cage surface (like about .005") that shouldn't be a problem crank case pressure will close them. All my race engines have the reeds not touching the cage surface. Though strange that they raised over night?

What engine are you working with?

Not familiar with the CCM reeds you are using are they single petal or multiple petal cut? How did you align the reeds on the cage to be parallel to the reed openings ( am thinking oval reed port openings not circular hole openings)?

[grayson]

If you mean they are slightly raised above the reed cage surface (like about .005") that shouldn't be a problem crank case pressure will close them. All my race engines have the reeds not touching the cage surface. Though strange that they raised over night?

What engine are you working with?

Not familiar with the CCM reeds you are using are they single petal or multiple petal cut? How did you align the reeds on the cage to be parallel to the reed openings ( am thinking oval reed port openings not circular hole openings)?

30 Yamaha 3 cyl, they are only slightly raised, probably the oil drained away overnight, the gap was tiny, but I like the reeds to seal with no light showing. Multiple/ twin petal cut, I tried them with factory reed stops then no stops but a flat rectangular plate with no stops.
They will probably run ok but I really want them to shut

[BJuby]

I use CCM reeds on all of my mercury restorations and quincy looper projects. Most of the time they tighten down with a small gap on a lapped cage. They run beautifully.

[zul8tr]

Like I and BJuby said no problem with a slight lift, they will seal with CC pressure.

BJuby what CCM reeds do you use, he offers 3 types: Drag, Sport and I think Performance? I suppose there are different thicknesses to each but same material? Any issues with tip frays or breakage ?

[DuckLn]

I've lapped several yamaha 30 and 40/50 2 stroke reed cages with success. You have to be somewhat reserved with the amount of pressure you apply when using sandpaper (I use 320 and then 400) but they have all laid flat for me afterwards. If its a 30 go ahead and get the 40/50 cages they fit without crank interferrence or have on the ones i've seen.

[BJuby]

Like I and BJuby said no problem with a slight lift, they will seal with CC pressure.

BJuby what CCM reeds do you use, he offers 3 types: Drag, Sport and I think Performance? I suppose there are different thicknesses to each but same material? Any issues with tip frays or breakage ?

I would have to check the order history. I think my loopers got a different thickness, but marginally. No I have not seen any fraying or issues. I ran the appropriate reeds in my 20H conversion fresh rebuild and my "A" Quincy Looper. Both run great.

[champ20B]

If the engine starts up and performs adequately, then they are O.K....

What you have are "racing reeds". Any good race/high output engine (with reed valves) are going to be raised a bit. The return spring action of the petals under operation bounces them shut and crank-case pressure keeps them shut. The idea of raised reeds is to allow easier intake flow for high RPM applications. Only on low pressure, small and mild fishing motors are seated reeds better. If it were an old 5 or 10 hp fishing motor, raised reeds might be hard to start the motor. But with bigger and modern high output motors with tight crank-cases, raised reeds are a real go to option. Just leave it as is and note the difference in performance. If its the same, try a slightly bigger carb and see if that helps. That's what them reeds are for.

[grayson]

well maybe i'll give them a run, still might spend a bit more time getting them to seal, maybe less pressure with the screws.

thanks everyone for the replies

[Fastjeff57]

The only problem with reeds not sealing happens when dirt gets under the reeds at the mounting point (and won't blow out in run).

Guess how I found THAT out!

Jeff

[grayson]

I've lapped several yamaha 30 and 40/50 2 stroke reed cages with success. You have to be somewhat reserved with the amount of pressure you apply when using sandpaper (I use 320 and then 400) but they have all laid flat for me afterwards. If its a 30 go ahead and get the 40/50 cages they fit without crank interferrence or have on the ones i've seen.

You know my problem may just be that I used 1200 grit. Probably not enough grit, I'll have another go with 400 then 600, if they are still out I'll try 320.

[zul8tr]

well maybe i'll give them a run, still might spend a bit more time getting them to seal, maybe less pressure with the screws.

thanks everyone for the replies

I would put the screws in at the proper torque and use thread lock. Check the bottom of the stops for perfect flat, can dress that area with 500 on flat table. I still wouldn't concern over the reeds up about .005" as said enough case pressure to close them.

[grayson]

I would put the screws in at the proper torque and use thread lock. Check the bottom of the stops for perfect flat, can dress that area with 500 on flat table. I still wouldn't concern over the reeds up about .005" as said enough case pressure to close them.

would you be able to tell me the correct torque? i used thread lock too

[champ20B]

I have a Yamato-80 racing engine. All eight of its reed petals are raised about 1/16" of an inch off the blocks. A long while back, I e-mailed Rick Montoya about this and he said that it was normal for this engine. He was right!
Not only does the engine start in one pull under load, but the darned thing actually idles as good if not better than any fishing motor I have ever owned except for my 1958 Johnson 7.5hp.....The performance is super as well (65mph, no problem). I attribute this to raised reeds. It can easily pull in gulps of air at full power because of this and its got it!

[zul8tr]

I do not know the Yamaha torque spec for the reed stop bolt but for the older Mercs most models are 35 to 40 inch-lb (not ft-lb).

[zul8tr]

The rougher grit will also hold oil and help to cushion the reed landing on the cage which is quite forceful high rpm. For my SS race Merc I use 180 wet on a flat glass plate (Merc has an aluminum cage). I sand it in 2 directions at 90 degrees from each other to make a hatch grid (per Jerry Wienandt, but he uses a coarser grit for his Merc race engine builds)

[Xpress2830]

Hey Grayson hows it goin. Bobby here from Louisiana. I have alot of trial and error with the Yammi 30 3-cylinder. Is this motor stock?? I had a 1998 25 3-cylinder it ran bad. I removed power head and the powerhead gasket was leaking. I went ahead and installed a shortened 30 tuner ( cut off at water intake ), Tohatsu 40 carbs with ( .122 ) highspeed jets. I tried CCMS reeds I actually lost rpm over stock. Boyesen was a little better. This motor ran the best with a set of stock 40/50 reed cages. I hope this helps.Please let me know if I can help. You can e-mail me @ bobby.crochet@lyondellbasell.com...

[grayson]

Hey Grayson hows it goin. Bobby here from Louisiana. I have alot of trial and error with the Yammi 30 3-cylinder. Is this motor stock?? I had a 1998 25 3-cylinder it ran bad. I removed power head and the powerhead gasket was leaking. I went ahead and installed a shortened 30 tuner ( cut off at water intake ), Tohatsu 40 carbs with ( .122 ) highspeed jets. I tried CCMS reeds I actually lost rpm over stock. Boyesen was a little better. This motor ran the best with a set of stock 40/50 reed cages. I hope this helps.Please let me know if I can help. You can e-mail me @ bobby.crochet@lyondellbasell.com...
Hey Bobby, I think I have had a similar experience, I feel after trying ccm sport and the cfm race they maybe are too stiff for the little 30. Maybe if I had more compression than stock it would be better, but I went back to standard reeds and gained Rpm.
Going to try a set of doukas reeds next that are thinner than all of them, but still slightly stiffer than stock. Will keep them until I get my new shaved head with reshaped dome for more compression. I have tohatsu 40 carbs, 50 reed blocks too.

[champ20B]

about "high compression heads", between two and four cycle engines......

I see a lot of people emphasizing on making the cylinder [combustion chamber(s)] tighter.... Well, on a two cycle engine, this will make it so that a more high performance fuel can be used and with less advanced timing. But other than that, it is really about accommodating high rpm action. It will not help make the engine have a stronger intake like as so with four cycle engines. With four cycle engines (like muscle-car engines), having a tight chamber does more than accommodate fast burning fuels with higher psi. It also causes a stronger intake vacuum at the pull of the piston so that bigger cams and carburators can be used as well as other flow enhancements.

Having a high compression cylinder in a two cycle engine has a very minute advantage compared to a four cycle engine because only compression and power take place there. With a four cycle engine, you would get intake, compression, power, and evacuation all in just the cylinder.....not a separate area like the crankcase.

Basically, my point is that if you tighten up the crankcase on your two cycle engine, then that will increase the intake and induction strength. A tighter cylinder volume will increase compression so a higher octane fuel can be used with a change in timing, for the higher rpm that will result as higher HP is made.

[Fastjeff57]

True, but if the exhaust is properly designed, a LOWER crankcase vacuum (meaning a larger volume) will produce more power--especially if one is using a properly designed expansion chamber. Weird, but the reason why is this: There's more air/ fuel mixture in there for the exhaust pulse to suck in. More volume means more power.

In the case of poor exhaust suction, however, then a higher crankcase vacuum (smaller volume) makes more power since it helps expel the exhaust gases.

Jeff

PS: A well designed expansion chamber will pull air in by the reeds when the exhaust ports are wide open! The designers of dirt bike engines found that out in the late 70s when piston port engines were down on power compared to reed valve engines. The idea that reeds, being far more restrictive than an open port, would produce less power was blow away when their improved air flow late in the stroke was finally understood. Since then, no dirt bike engines have been piston ports.