Let's test your diagnostic skills

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rlkarren
Posts: 388
Joined: Tue Jul 23, 2013 6:50 am
Location: River Heights, Utah

Let's test your diagnostic skills

Post by rlkarren »

Someone else did this awhile back and I thought I'd have a little fun too... Winner gets a nearly new, low mileage, 42-year-old SH-83A pencil holder/paper weight, deliverable at HD15, as long as I can make it next year... And if you live in Deweyville, Utah, you are ineligible to play. ;-)

Anyway after returning from HD14 this year, I changed jetting back to what was installed previously for 4400 ft. But something was not quite right. My Wombat started acting up... here's the symptoms:

1. Initially, there was no power in the top gears. Plenty of power as expected in 1st - 3rd gear but sharply dropped off in 4th and 5th. Top speed at WOT was about 30 - 35 mph. This behavior kept getting progressively worse no matter what I cleaned/changed.

2. At WOT throttle, the motor felt as if the points were floating/four-stroking. Got the death rattle very quickly. (four-stroking with a death rattle, makes no sense)

3. Engine heated up real fast.

4. Starts and idles fine. Revs easy when not in gear, but as soon as you put a load on it, it bogs down fast.

5. Smaller or Larger jets made no change and sometimes it got worse, (larger jets).

6. Timing was correct. All specifications within spec.

7. Plug readings were on the lean side even with larger jets, and sometimes it was fine. Very inconsistent.

8. New piston and rings, known working ignition, and new seals, (crank seals left and right, counter shaft seal), made no change.

Carb was cleaned, (dip tank and sonic washer), and blown out twice. Timing was checked and re-checked multiple times between .013" - .015". Removing the air cleaner seemed to help but very nominally, checked for obstructions and found none. Head and cylinder gaskets were changed and checked for leaks and found none.

I did stumble upon the problem and was up and running very soon after. If some of these symptoms make no sense or confuse you, you have experienced some of the frustration I had when nothing worked! ;-)

What was the problem? I left you a clue...

Good luck!

Roger

PS: The bike is running great since I found and resolved the issue.
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Dale
Posts: 1259
Joined: Fri Jul 19, 2013 7:23 am

Re: Let's test your diagnostic skills

Post by Dale »

Plugged pipe?
Just in case that is it, I will pass on the carb... I already have one of those and one is enough.
Dale
Dale
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bchappy
Posts: 448
Joined: Fri Jul 19, 2013 6:46 am
Location: Monument, CO

Re: Let's test your diagnostic skills

Post by bchappy »

My guess is also plugged pipe. I had the same symptoms recently and cooking the pipe was the answer. Just about drove me crazy.
Bill Chapman, Monument, CO
Raced and Modified Hodakas in Statesville NC back in the day.
junker2k
Posts: 77
Joined: Sat Jul 20, 2013 11:41 am

Re: Let's test your diagnostic skills

Post by junker2k »

I would change the carb, just to be sure.
Jack K
rlkarren
Posts: 388
Joined: Tue Jul 23, 2013 6:50 am
Location: River Heights, Utah

Re: Let's test your diagnostic skills

Post by rlkarren »

man! you guys are good!

I forgot to mention I switched between two different carbs trying to eliminate that as the source of the problem and had no change.

Dale, I guess I'll just have to buy you a diet Pepsi.. next year at HD15 ;-) Can't believe you really don't want matching "His & Hers" Pencil holders.. ;-)

Yeap, plugged pipe. After cleaning the carb a 2nd time in the sonic washer, I re-installed it. After the first test ride showing no change again, and with no connection in my thoughts to the problem, the thought crossed my mind to take a look at the baffle. It took some doing because it was in there pretty good, but it finally came out and it had a ton of carbon and oily residue on it. Doug suggested I take it for a spin without the baffle and I knew that was the problem as soon as I took off. I didn't think to check it earlier because I had just cleaned it two weeks before HD14.

When I got home, I torched it until it was a dark red hot, both the baffle and the pipe. Took 30 - 45 minutes until the smoke subsided. It was plugged up pretty good.

Just returned from a 30 mi ride to test and the bike is happy now... just wants to go faster... ;-)

Roger
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Dale
Posts: 1259
Joined: Fri Jul 19, 2013 7:23 am

Re: Let's test your diagnostic skills

Post by Dale »

Roger, I will look forward to a cold diet pepsi then! I'm glad that you have it running well again.
Dale
Dale
MTRob
Posts: 220
Joined: Wed Nov 06, 2013 10:42 am

Re: Let's test your diagnostic skills

Post by MTRob »

Roger thats what my 94A Wombat is doing but I already cleaned the pipe had it powder coated and the inside pipe cleaned. Still working out my problem.
Thanks
MTRob
Zyx
Posts: 926
Joined: Sat Mar 22, 2014 4:41 pm

Re: Let's test your diagnostic skills

Post by Zyx »

Taking the stock baffle out entirely is always a good way to test for clogging. If you still have the stock spark arrester (the little spiral bullet) in there, mine always clogged fast so I took it out. Back in the 70's we were not worried about spark arresters, even when running in the National Forest. Things change.

I would be a bit concerned that it clogged up so fast if you had cleaned it just before going to HD, assuming that it was as thoroughly cleaned as you believe. Sounds like you were running really rich at HD, as in maybe you didn't need to change jetting at all, or perhaps you used a different gas/lube blend at HD than at home, and it ran dirty. Surely it takes more than a weekend to clog up the pipe.
rlkarren
Posts: 388
Joined: Tue Jul 23, 2013 6:50 am
Location: River Heights, Utah

Re: Let's test your diagnostic skills

Post by rlkarren »

Arizona Shorty wrote:I would be a bit concerned that it clogged up so fast if you had cleaned it just before going to HD, assuming that it was as thoroughly cleaned as you believe. Sounds like you were running really rich at HD, as in maybe you didn't need to change jetting at all, or perhaps you used a different gas/lube blend at HD than at home, and it ran dirty. Surely it takes more than a weekend to clog up the pipe.
It is some concern that it clogged up so fast. I'll be watching it for the next couple weeks. I have a feeling that it was that last tank of gas before leaving Athena for Utah. I neglected to fill the can earlier on Friday night so I had to go all the way to north of Milton-Freewater to get gas. Your thought of a different gas/lube, I think, is right on the money.

MTRob: I would suggest trying to find a known-working ignition to test and a known-good carb with standard jetting. I've found that ignition and carb issues are really difficult to pin down unless you've got lot's of experience. I'm still a novice... ;-) My biggest fear was throwing money at a problem until it went away, which is really easy to do. Luckily, mine wasn't too expensive.

Roger
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