1975 Harley model D4 no power

sparksstevep

Hello:
I have a 1975 Harley model D4. The engine starts and runs at idle fine. 1) Will not rev up when I press the accelerator. I have replaced the carburetor and gas line thinking it was not getting good gas flow. 2) The drive belt slips on the drive clutch v belt plates under load. I have replaced the v belt, replaced the v belt plates on both the drive and driven clutches and replaced the springs in both clutches. The clutches work fine when I jack up the rear of the cart and observe the gear ratio changes.

Any suggestions?
Thanks.

BGW

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tew45

Your cart is not idling! Your starter motor is running and trying to start the engine. Do you have spark? What is your compression reading? Have you tried a little fuel in the combustion chamber? check those and get back to the forum.
Remember it takes; (1) a spark at the right time (2) proper compression (3) fuel
If all three of these are present, I can't help you.

sparksstevep

Hello:
my 75 D4 2 cycle Harley starts, idles and revs up easily but it seems that the RPM's are not as high as they should be. If I block the wheels, at max rpm the drive belt slips at the drive clutch. It seems that the engine does not have enough RPM to fully engage the drive clutch. As the cart moves forward, it is slower than a walking pace at max speed and will not pull a hill of any kind. Going up a hill the engine does not lug down or slow. The engine seems to have plenty of power but it is not getting transferred to the wheels. Again, it seems that the drive belt is slipping at the drive clutch just like it is when I block the wheels.

If I jack up the rear end, the clutches can be seen to changes based on RPM's just fine. Under a load, the belt slips.

I have looked for a governor but can not find one anywhere.


I have done the following-one at a time, then checked the results.

1. replaced the drive belt- no change.
2. removed the washer spacers in the drive clutch- no change.
3. rebuilt the drive clutch- guides, springs, bushings etc. as it had some broken parts- no change.
4. replaced the drive clutch pulley plates as they were cupped- no change.
5. Rebuilt and replaced cupped plates and springs on the driven clutch- no change.
6. checked the gas tank air vent and check valve on the gas pick up line. all is fine.- no change.
7. Replaced fuel line from tank to carburetor- was old and squishy. Checked fuel filter- clear- no change.
8. Cleaned the carburetor- no change.
9. replaced the carburetor- no change. Carburetor is not sensitive to adjustment... hum...
10. installed a fuel pump. Fuel flow is fine-- no change. Still not sensitive to carburetor adjustments. ( I am running between 1/2 turn open to 2 1/2 turns open with almost no change). I am set at 1 turn now.

11. Compression is between 80 and 85 psi.
12. Points are between .020 and .022.
13. Cleaned and gaped the spark plug to .028-slight RPM change.
14. Checked the coil- it jumps about 1/2" gap.
15. took the muffler off and ran it off- no change.

I don't know what else to check.
Thank you for your insight.

tew45

Is your timing correct? Your carb adjustment is the low speed jet so it should not cause any change at anything except very low RPM. I usually set the points at .024 in most cases.

AKAMick

Check intake reed valve

AKAMick

Got the correct size belt on it?

tew45

Pull the drive belt off and see if the primary clutch is working. If the engine will run at high speed with wheels off the ground and the primary clutch slips the problem is in the drive system one or both clutches are not working. Check the rear end and wheels for free turning with the drive belt off. I usually set the low speed jet(only carb adjustment) at 3/4 turn out. The cart has no idle so it makes little difference. The points are .022 to .024 which allows foe some point rubbing block wear which is minimal if quality point set is used and the block is lubricated

sparksstevep

Ready to shoot this Harley!

I have run out of ideas on getting this old Harley to have some speed. I don't expect break neck speeds but top speed on level ground is not as fast as a brisk walking pace and slows to less than walking speed going up a slight incline.


Today I adjusted the timing and forward and reverse have the same low speed. the Spark was orange so I replaced the condenser, coil and spark plug wire, still no change.


I have checked the clutches after I repaired and replaced the parts in them and they work fine when the rear end is jacked up.

I have either checked or replaced almost everything... I am out of ideas so any help would be appreciated.

Thanks for the previous replies.

sparksstevep

Oh, I have also replaced the reed valve and the drive belt.

AKAMick

Seems like you have everything covered, This is a puzzle for sure, there is something that is amiss, there is no voodoo to engines so something is still not right, has the engine a good solid ground, what ohm coil did you use, ballast resistor on your unit? run a hot lead from the battery to the coil to eliminate a high resistance in that. brake not dragging, though I think you would have checked that, Hmm!