Ironhead Only 4th gear not engaging?

[Hardtail28]

Well, let me first begin if I may, by thanking all of you who have helped me before. Thanks very much!!! Today I was riding just quickly down the street.. I was on a straight-way and already in 4th gear. I decided on giving it a quick "blip" and kept with the fast speed for about 4 or 5 seconds before it suddenly acted like an intake boot became super-SUPER loose and wouldn't run (I believe I also may have heard a faint chain-rattling type of sound as well). I down shifted and got home (which was only about 100 feet away). I decided to restart the bike and take it back out to see it's behavior. I only rode it about 300 feet but ,It seemed to shift up and down just fine, only won't accel when I shift it into fourth.. I have to shift it back into a lower gear to actually go anywhere. I thought that it was a clutch problem but, a friend of mine said that, "that has nothing to do with the clutch". I will expose my ignorance and admit that I have absolutely no idea if it is not a clutch issue.. if anyone could help point me in a good direction or has any idea what it could be, I'd be extremely grateful. Thank you for reading.

[1Scooter]

It's time to pull the trans out for inspection and repair.

[Hardtail28]

Man! I just bored the jugs, did the heads,pistons, etc. But yeah, you probably hit it correctly..I've never done it before.. pretty evolved/expensive for replacement? Thank you for your reply by the way, you are the only one who did I surely do appreciate it

[needspeed]

If I read your post correctly it shifts OK into all gears, including 4th, but just won't accelerate in 4th. If that's true then it's premature to suggest pulling the transmission.

Some more questions and answers are needed first.

Does the engine rev up when opening the throttle in 4th but just not accelerate? Does it still make that noise?

[Hardtail28]

Yes.. the engine does Rev when in 4th and trying to accelerate... it just doesn't respond by faster movement. I have taken it out 2 times since (very short rides, about 300 feet) and I have not heard that sound. I think that it actually (may) slow down briefly just for a split second when in 4th and attempting to accelerate. It may be also in my head.. that it kind of gets a groggy type sound? Anyhow, if you are able to think of something that may work other than pulling the transmission.. I would be greatful.thanks

[joe s]

Sounds like it could be a slipping clutch, and maybe the key sheared and that's the noise?

[ericfreeman]

Clutch slipping is a good place to start. My old '77 used to slip in 4th going up a hill. Engine would rev up but speed wouldn't increase. Clutch is under the highest stress in 4th gear and is most likely to slip then.

[sungod]

Can you add some load in the other gears like going up a big hill and see if you have slippage? The clutch should operate the same in all gears. My guess would be 4th gear is not fully engaged which will require a deep dive.

[Monte03]

*Suspect Worn Rounded Corner Male Dogs on the Bottleneck Clutch Gear , ‘ask me how I know’ it was Dr Dick that rebuilt my 68 H trans, and we installed a rare C ratio bottleneck ( the long one ) , no more pulling out of 4th..

[ryder rick]

Too much mainshaft end play.
Bent shift fork.
Worn dogs.
Wrong shift fork.
Pawl support bad?
Bad shift linkage.

Poor clutch adjustment.

Get the clutch right before addressing any trans issues.

They don't call me Ironhead Rick just because I'm hard headed