Hi everyone, long time no see. I finally got the 'Forgotten 91 TDM' on the road last Monday. Have to say it is one incredible machine, except for one rather irritating and potentially dangerous problem: it backfires like nobodies business on deceleration. (potentially dangerous because horses gallop immediately upon hearing it!)
It will pop VERY loudly until I either roll on the throttle again or come to a stop altogether. The revs also tend to sink immediately after riding at speed then rise up again to 1000rpm, sort of as if it clears some excess fuel out that is hanging around.
I'm led to believe it may be a pilot jet issue or possibly the fuel level is set incorrectly. To be honest I haven't a clue about carbuerration so any advice would be greatly appreciated. (I've virtually eliminated to possibility of the exhaust blowing which was a previous suggestion, it sounds spot on and I can't feel any air blowing out anywhere)
Thanks!
Backfiring is getting dangerous...
Started by
tdm850tdm
, May 03 2006 08:37 pm
16 replies to this topic
#2
TDMTAM
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- Location:Glasgow, Scotland
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Posted 03 May 2006 - 10:54 pm
QUOTE(tdm850tdm @ Wed 3rd May 2006, 09:22 PM) <{POST_SNAPBACK}>
Hi everyone, long time no see. I finally got the 'Forgotten 91 TDM' on the road last Monday. Have to say it is one incredible machine, except for one rather irritating and potentially dangerous problem: it backfires like nobodies business on deceleration. (potentially dangerous because horses gallop immediately upon hearing it!)
It will pop VERY loudly until I either roll on the throttle again or come to a stop altogether. The revs also tend to sink immediately after riding at speed then rise up again to 1000rpm, sort of as if it clears some excess fuel out that is hanging around.
I'm led to believe it may be a pilot jet issue or possibly the fuel level is set incorrectly. To be honest I haven't a clue about carbuerration so any advice would be greatly appreciated. (I've virtually eliminated to possibility of the exhaust blowing which was a previous suggestion, it sounds spot on and I can't feel any air blowing out anywhere)
Thanks!
It will pop VERY loudly until I either roll on the throttle again or come to a stop altogether. The revs also tend to sink immediately after riding at speed then rise up again to 1000rpm, sort of as if it clears some excess fuel out that is hanging around.
I'm led to believe it may be a pilot jet issue or possibly the fuel level is set incorrectly. To be honest I haven't a clue about carbuerration so any advice would be greatly appreciated. (I've virtually eliminated to possibility of the exhaust blowing which was a previous suggestion, it sounds spot on and I can't feel any air blowing out anywhere)
Thanks!
I would try checking all the exhuast joints as it can be an air leak in to the system
TAM
2008 TDM 900 in BLACK, MRA Vario, DL handguards & more to come
1994 TDM 850 mkI Silver, with Blueflame end can, Gone to a new owner & I kinda miss her!
Only a Biker knows why a Dog sticks it head out the car window
Only a Biker knows why a Dog sticks it head out the car window
#3
duibhce Kaelann
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Posted 03 May 2006 - 10:59 pm
sounds more like a problem witrh the combustion mix. Perhaps the mix is a bit lean, or -more likely- too rich.
Yamaha XT660Z Ténéré '08 + Yamaha TRX850 '97
I'll let go of my throttle when they pry it from my cold, dead hands...
#4
tdm850rider
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Posted 03 May 2006 - 11:01 pm
QUOTE(TDMTAM @ Wed 3rd May 2006, 05:39 PM) <{POST_SNAPBACK}>
I would try checking all the exhuast joints as it can be an air leak in to the system
TAM
TAM
agree with the above.. when my 92's header pipes got a hole in them it pop'd quite a bit... got very loud as well.
btw.... what are those 2 8mm bolts in the bottom of the header? drain plugs or what?
Always tell the truth, it will gratify some of the people and astonish the rest. (Mark Twain)
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#5
dandywarhol
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#6
tdm850tdm
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Posted 04 May 2006 - 07:38 am
Thanks for the thoughts guys. It's got a full micron system, could the loss of back-pressure from the standard exhaust have anything to do with the problem?
I will double check that it's not leaking anywhere.
Thanks
I will double check that it's not leaking anywhere.
Thanks
#7
aytcat
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Posted 04 May 2006 - 11:02 am
Dont know if this will help,i had a brand new TTR600RE before i swoped it for the TDM, that use to back fire on the overun i checked the plugs for their colour and was running lean on idle so everytime i closed the throttle it backfire like crazy,I increased the idle revs as much as i dared but it improved it a bit.
In the end i i increased the number of turns out on the pilot air mixture screw with the engine running at standard idle and revved the engine and shut the throttle quick and adjusted the screw till the backfire almost disapeared.but couldnt get it to disapear completly.but it only done it now and then. Checked the plugs again and they were a tan colour rather than the near white cause of the leaness of the fuel mix
In the end i i increased the number of turns out on the pilot air mixture screw with the engine running at standard idle and revved the engine and shut the throttle quick and adjusted the screw till the backfire almost disapeared.but couldnt get it to disapear completly.but it only done it now and then. Checked the plugs again and they were a tan colour rather than the near white cause of the leaness of the fuel mix
Edited by aytcat, 04 May 2006 - 11:05 am.
#8
tdm850tdm
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Posted 04 May 2006 - 09:52 pm
Gonna remove and refit the entire exhaust system with plenty of fire putty this weekend, see what that can sort out.
Failing that I'll have to try aytcat's suggestion which sounds promising (although I wouldn't want to do it without eliminating the possibility of an exhaust leak first, the last thing you want to do is start covering up problems).
Thanks everyone
Failing that I'll have to try aytcat's suggestion which sounds promising (although I wouldn't want to do it without eliminating the possibility of an exhaust leak first, the last thing you want to do is start covering up problems).
Thanks everyone
#9
aytcat
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Posted 04 May 2006 - 10:49 pm
Try this link it tells you the causes of backfire in excausts http://www.mikuni.co...ning_guide.html
#10
tdm850tdm
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Posted 05 May 2006 - 07:46 am
QUOTE(aytcat @ Thu 4th May 2006, 11:34 PM) <{POST_SNAPBACK}>
Try this link it tells you the causes of backfire in excausts http://www.mikuni.co...ning_guide.html
Massively helpful aytcat, thanks very much for that
I noticed that the air intake to the right-hand carbuerretor has been repaired at some point in the past so I'll check that and make sure it's not leaking there as well.
#11
tdm850rider
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Posted 06 May 2006 - 01:43 am
QUOTE(aytcat @ Thu 4th May 2006, 05:34 PM) <{POST_SNAPBACK}>
Try this link it tells you the causes of backfire in excausts http://www.mikuni.co...ning_guide.html
Maybe that link should be added to The Depository?
Always tell the truth, it will gratify some of the people and astonish the rest. (Mark Twain)
£
Stebel Nautilus air-horn, Corbin seat, MRA Touring screen, single Delkevic silencer.
"I see by your outfit that you are a spaceman"(MkI (3VD) TDM Review)
Hints for using Carpe-TDM. (photo's, links, etc).
#12
tdm850tdm
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Posted 06 May 2006 - 05:37 pm
QUOTE(tdm850rider @ Sat 6th May 2006, 02:28 AM) <{POST_SNAPBACK}>
Maybe that link should be added to The Depository?
Agree with that, very 'newbie friendly'.
Anyways, thanks for all the suggestions everyone.
Got some standard silicone sealant this morning which is suppose to be stable up to about 200 degrees to seal the end can (as it seemed to be blowing a fair bit there). Also changed oil and filter this morning btw.
I notched up the idle speed about 200rpm (was a bit low anyway) and went for a test ride. Work brilliantly for about 10 mins, just burbling lightly under heavy engine braking - great sound.
After this the backfiring started creeping back in more and more until it was actually worse than before. Getting off the bike I see sealant evaporating for the end can joint, and it stinks!
Went down to halfords and picked up some loctite silicon gasket sealant that's supposedly good for 350 degrees. I'm just leaving that to set for a few hours now, having removed and refitted the end can yet again. Hoping this will be the solution to my problems!
#13
tdm850rider
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Posted 06 May 2006 - 05:46 pm
QUOTE(tdm850tdm @ Sat 6th May 2006, 12:22 PM) <{POST_SNAPBACK}>
Agree with that, very 'newbie friendly'.
Anyways, thanks for all the suggestions everyone.
Got some standard silicone sealant this morning which is suppose to be stable up to about 200 degrees to seal the end can (as it seemed to be blowing a fair bit there). Also changed oil and filter this morning btw.
I notched up the idle speed about 200rpm (was a bit low anyway) and went for a test ride. Work brilliantly for about 10 mins, just burbling lightly under heavy engine braking - great sound.
After this the backfiring started creeping back in more and more until it was actually worse than before. Getting off the bike I see sealant evaporating for the end can joint, and it stinks!
Went down to halfords and picked up some loctite silicon gasket sealant that's supposedly good for 350 degrees. I'm just leaving that to set for a few hours now, having removed and refitted the end can yet again. Hoping this will be the solution to my problems!
Anyways, thanks for all the suggestions everyone.
Got some standard silicone sealant this morning which is suppose to be stable up to about 200 degrees to seal the end can (as it seemed to be blowing a fair bit there). Also changed oil and filter this morning btw.
I notched up the idle speed about 200rpm (was a bit low anyway) and went for a test ride. Work brilliantly for about 10 mins, just burbling lightly under heavy engine braking - great sound.
After this the backfiring started creeping back in more and more until it was actually worse than before. Getting off the bike I see sealant evaporating for the end can joint, and it stinks!
Went down to halfords and picked up some loctite silicon gasket sealant that's supposedly good for 350 degrees. I'm just leaving that to set for a few hours now, having removed and refitted the end can yet again. Hoping this will be the solution to my problems!
exhaust temperatures get very high... if that does not work just get the hole welded shut.
Always tell the truth, it will gratify some of the people and astonish the rest. (Mark Twain)
£
Stebel Nautilus air-horn, Corbin seat, MRA Touring screen, single Delkevic silencer.
"I see by your outfit that you are a spaceman"(MkI (3VD) TDM Review)
Hints for using Carpe-TDM. (photo's, links, etc).
#14
dapleb
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Posted 06 May 2006 - 06:03 pm
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If you want to mark your location on the Carpe map: http://www.carpe-tdm...opic.php?t=5117
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If you want to mark your location on the Carpe map: http://www.carpe-tdm...opic.php?t=5117
Doin valve clearances? Use dappers valve shim exchange program and the job will be carroty - Free (other than you postin me yer shims) for sporting members.
Active member of TPLQHCSRSFC and TSRMCMAS (even though a year off) and avid fan of PM not sent.
#15
ChrisG
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Posted 06 May 2006 - 11:01 pm
QUOTE(tdm850tdm @ Sat 6th May 2006, 06:22 PM) <{POST_SNAPBACK}>
Went down to halfords and picked up some loctite silicon gasket sealant that's supposedly good for 350 degrees. I'm just leaving that to set for a few hours now, having removed and refitted the end can yet again. Hoping this will be the solution to my problems!
Is the the coper coloured stuff? I used that on mine for the exhausy gaskets and the join between the header pipes and the centre section and it works really well.
1992 Mk1, 76k miles, Hagon springs, MTC exhaust, 4½ gears Gone now 
2009 900 abs, 42k miles, Yamaha heated grips, double bubble screen, R&G crash bungs, scottoiler, Autocom, 1500 lumen LED spotlights.
#16
Guinness
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Posted 07 May 2006 - 07:41 am
QUOTE(tdm850rider @ Sat 6th May 2006, 02:28 AM) <{POST_SNAPBACK}>
Maybe that link should be added to The Depository?
copy&pasted the entire article into the Depository
copyright and all...
I'm an insomniac agnostic dyslexic. I lay awake at night and wonder if there really is a dog.
yamaha : xv535/92-92 | red TDM850/92-05 | silver TDM900A/05-
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yamaha : xv535/92-92 | red TDM850/92-05 | silver TDM900A/05-
get them here
#17
tdm850tdm
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Posted 09 May 2006 - 09:35 pm
PROBLEM SOLVED!
Thanks for all the advice everyone who chipped in, in the end a guy on another forum pointed out the obvious.
I removed the carbs today and took them down to PDQ Motorcycle Developments, Taplow, to get new emulsion tubes fitted. They did it while I waited (took 30 mins) and the bill came to £65.45 - a lot cheaper than 3 hours of dyno time that wouldn't even have solved the problem Very Happy . Top blokes down at PDQ, with top advice as well (although their dyno is booked until the middle of June
)
Anyway, the project is now finished, I'll post some pictures soon. Now all I have to do is decide whether to keep it or sell it and get a mk2. I kinda feel like keeping it really cos this bike now has all the problems ironed out, whereas you don't know what you're getting with a new bike. Hmmm
Thanks for all the advice everyone who chipped in, in the end a guy on another forum pointed out the obvious.
I removed the carbs today and took them down to PDQ Motorcycle Developments, Taplow, to get new emulsion tubes fitted. They did it while I waited (took 30 mins) and the bill came to £65.45 - a lot cheaper than 3 hours of dyno time that wouldn't even have solved the problem Very Happy . Top blokes down at PDQ, with top advice as well (although their dyno is booked until the middle of June
)Anyway, the project is now finished, I'll post some pictures soon. Now all I have to do is decide whether to keep it or sell it and get a mk2. I kinda feel like keeping it really cos this bike now has all the problems ironed out, whereas you don't know what you're getting with a new bike. Hmmm
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