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Discussion Starter · #1 · (Edited)
Need help, very sluggish 748 engine (fixed)

I was riding my 748 yesterday (10k miles), everything was running well as normal. Just did a valve adjustment ~300 miles ago. Came to a stop at a stoplight, then upon takeoff the engine became extremely sluggish and would hardly accelerate. Before this I was riding very normally, no WOT or any sort of "sporty" riding. Once above around 4k RPM the engine would all of a sudden kick in and operate like normal. The engine makes a much lower and underpowered sound when this sluggish behavior happens, but sounds normal when power comes back. I pulled the plugs, both seem decent. Horizontal plug had a little oil on it, vertical seemed to have some condensed water? Also, the vertical spark plug wire seems to have been broken at the end and taped by the PO. Any ideas or suggestions? Let it sit for a day, still does the same. Like I said, the engine is much quieter and has a lower tone. It seems like the engine is all of a sudden very far off for being tuned, some problem with injectors or A/F ratio? Both cylinders work, no CEL, oil is good (just changed 1 month ago). Timing belts need to be done, waiting for Ca-Cycleworks on that one.

EDIT: Problem fixed, condensation in vertical spark plug cavity caused the issue.
 

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Mayor of Simpleton
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First, replace those garbage wires. You can get the upgraded TPO Dragon ones on eBay for $40. No excuse for ignoring something like that whether its causing the problem or not. Given the sudden onset, I don't think its a real tuning issue. I think its probably is electrical--wires or coils first, then move on to charging system.
 

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Discussion Starter · #3 ·
Yep, the first thing I did when I saw the bad wires was get online and order a new set. Hopefully they will be here in a couple days. Is there a way I can test the coils now using a multimeter or anything?

EDIT: Also, the road was 1/2 wet when this started happening. One area of town must have gotten a little rain, and the pavement wasn't dry. Could the tires have kicked up some water and ruined an electrical component?
 

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I had the same problem with mine, it's water getting into the plug cavities and caused a bad connection.
When you install your new leads, you can put some sparingly on the leads to seal then to the cam covers, this will stop water egress.
 

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Discussion Starter · #5 ·
Desmogod, I'll have to try that when the new wires come in. As mentioned in the first post, there was some water around the vertical spark plug wire and spark plug. Also, you said "put some sparingly on the leads to seal them to the cam covers". What am I supposed to put on sparingly?
 

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Yeah, moisture is a very likely contributor. The new plug wires take care of that too though since they include new spark plug boots.

I think the coils are OK. They don't have a reputation for failing.

I have a V8 Lincoln LS which uses individual coils in each plug wire/cap. Great, as there's never a distributor to replace... Not so great when these cars are NOTORIOUS for leaking valve cover gaskets. Moisture gets into the plug wells, shorts out a coil or three, and then you pretty much have a $500+ repair bill.
 

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Discussion Starter · #8 ·
Desmogod got it, 2 points for you. I let the vertical spark plug wire dry out and dried off the spark plug, put it back together, now it works like a charm. Desmogod, can you explain better how to keep moisture from getting in the plug cavities?
 

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What you need is the 853 kit...sluggishness be gone! :)
 
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Desmogod, I'll have to try that when the new wires come in. As mentioned in the first post, there was some water around the vertical spark plug wire and spark plug. Also, you said "put some sparingly on the leads to seal them to the cam covers". What am I supposed to put on sparingly?
I'm sorry mate!
Was late and I must have missed what I meant to type.
Use some high temp silicone and smear some around the mating surface of the plug lead and spark plug hole, this should seal it against water and won't be a pain to get off in the future.

What you need is the 853 kit...sluggishness be gone! :)
Or a 996 kit ;)

EDIT: Just to clarify, you only need a small bit on the surface indicated, not too much or you'll never get the plug leads off again, RTV or theeebond should be fine.

Also, I believe in the states you can get a silicone based ignition system sealant in a spray can that seals your electrics, although I have no idea how this would fare on a motorbike.
If it's good, I'd kill for a can and do my entire ignition system in it.
 
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