Author Topic: engine sounding like a 'diesel' at low revs.......wtf?  (Read 2627 times)

Offline singleoverheadbraincell

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engine sounding like a 'diesel' at low revs.......wtf?
« on: October 03, 2012, 11:01:12 AM »
I have this bike only about a month now and have been tinkering with various things up until now, except the carb settings. I did suspect that it was ticking over a bit high (around 1400) and checked the manual which verified that tickover should be 1000rpm (550K). I turned the thumb screw outward to lower the idle only to discover to my horror that the engine started to sound like it was a diesel. My initial thought was that it sounded like a small end bearing. The noise disappears though at revs around 1400 or above so I set about adjusting the timing chain. I adjusted the timing chain using the method (described in this forum) of putting a little bit of tension on the chain with the kickstarter after TDC on cylinder#1. Anyway, this seemed to help it a little bit but the noise has not gone away. My only solution (at least for the symptoms) is to raise the idle to around 1400.

I haven't yet cleaned or balanced the carbs and I know this could help matters and I know also (from my reading) that these bikes are prone to a bit of low end rattle but I'm just not sure it should be as noisy as this. I understand the cam chain can be changed with the engine in-situ by attaching the new chain to the old chain and drawing it round and I would be prepared to undertake the surgery - I'm just wondering if this would improve matters or would I need also a new tensioner (these are pricey!) I don't really mind living with the issue (by keeping the tickover around 1400) as long as the chain doesn't break, which would be a disaster. The bike has 44k on the clock and I just changed the oil/filter using 10W40 mineral oil.

Any thoughts/feedback most appreciated.

Offline mick

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Re: engine sounding like a 'diesel' at low revs.......wtf?
« Reply #1 on: October 03, 2012, 12:04:25 PM »
Hi your best bet is to give it a full service then at least you will know everything has been done, i have a  750 and believe me they can sound like a bag of spanners in a tumble dryer when the carbs need balancing etc  ;), cheers Mick. 

Offline Bitsa (Ralph Wright - RIP)

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Re: engine sounding like a 'diesel' at low revs.......wtf?
« Reply #2 on: October 03, 2012, 03:06:49 PM »
With Mick on this even worse without the clutch pulled in.
Cheers
Bitsa
Long Live Best Bitter.Status Quo and Sohc Bikes and common sense which you can not teach

Offline Bryanj

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Re: engine sounding like a 'diesel' at low revs.......wtf?
« Reply #3 on: October 03, 2012, 04:15:00 PM »
Forget the book, any tickover below 1200 is a dream, just about guarantee if you give it a full service then check the carbs it will get loads better

Offline madoc

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Re: engine sounding like a 'diesel' at low revs.......wtf?
« Reply #4 on: October 14, 2012, 10:52:33 PM »
I just changed my camchain.
I don't think it needed doing that badly, but as the head was off then NOT to do it would have been silly (along with changing the rings).
You can do a proper rivet job with the chain if the barrels are off - it's a real fiddle with the head in place.

It didn't quieten it down that much.

I'd echo what everyone else has said though.
I have vacuum gauges (I have a selection of boxer type engines) and it's stunning how much difference it makes at idle.

800 revs ?
I cannot get a reliable tickover at less than 1200/1000.  It stumbles and catches ( and sounds horrible when cold)

« Last Edit: October 14, 2012, 10:56:13 PM by madoc »

Offline florence

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Re: engine sounding like a 'diesel' at low revs.......wtf?
« Reply #5 on: October 16, 2012, 09:20:32 AM »
It is worth bearing in mind that all of these 500/550s sound rough at low revs even when they are set up correctly and all parts in good order.  I had a genuine 7000 mile engine with replacement cam chain, tensioners etc and it sounded like all the others I have heard, i.e. like a bag of nails, but increase the revs slightly and all extremely smooth.  17 years later and it sounds exactly the same, no worse.

I don't think they are really designed to run at low revs.  When I adjust the tickover there seems to be a sweet spot which I run up to.  My rev counter is broken but I think it is about 1200 revs.  Just remember, if you have the tickover too slow you won't have as much oil going up to the top ;-)

(maybe you can get them to run slower with stock airbox, exhaust and electronic ignition)

 

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