Spark Plug Length on 350
Posted: Sat Jan 12, 2019 11:26 am
Hi Guys,
OK, I am a bit of a newbie here.....and I admit that it is around 40 years since I last took a Ducati single apart, so what little knowledge I had then has long been lost! You will find a short introduction to me and my scrambler in the 'People pics' section.
I have a bundle of questions, and I am sure most will be pretty basic or even daft, so bear with me, I will start with two that are bugging me and slowing progress:
Sparkplug length:
I have a 1971 350 Scrambler and am a little perplexed by how high in the threads the sparkplug (Standard = B7HS) seems to lie, so deep that it appears to be totally covered by the threads. This was noted in a post by bikester250 back in Jan 2019, but no-one seemed to be forthcoming with any thoughts on this, so I wondered if I could ask again. Is this normal, Is it a problem and what is best way forward.
I have the additional problem that this head has a rather industrial thread-insert that has a 2.5mm collar on top, which therefore lifts the plug further still up the threads.
Although the engine runs OK, this doesn't look right to me and I am trying to work whether to ignore, use a different plug or try something different. As bikester250 pointed out, using a projected plug (B7PHS) will go some way to correct this, but with the insert, it will still be pretty low. Going to a 3/4in reach plug (B7ES) is a big jump and I worry will be too long, unless I used a washer above the insert, to raise the plug a couple of mm more. This could be a loose washer, or if I was confident of how it would work, I could solder a copper washer onto the top of the brass insert, making it permanent, but of course would need to do this before returning it (hopefully permanently) into the head. Any thoughts on any of these questions would be appreciated. What is the best way forward?
Removing the Bevel tube from head:
I realise this question will be pretty basic and I am sure a little gentle research would answer the question, but as I have your ear... I have the head off and want to remove the bevel tube to replace the failed gasket between it and the head. The Haynes manual seems to suggest it will just 'come off' leaving the bevel shaft it place, but if so, it needs a knack or method I don't have. Never been good at puzzles, but it looks to me like the bevel shaft/bearing is going to have to come out to allow me to remove the tube. So first, is there a way of removing the tube without the shaft? If not and the shaft has to be removed first, what is the best way to get it out. Manual suggests tapping it out from above, which I can understand, but never like pushing/hammering when the bearing is taking the pressure. What is the safest way to remove it?
Thanks in advance
eib
OK, I am a bit of a newbie here.....and I admit that it is around 40 years since I last took a Ducati single apart, so what little knowledge I had then has long been lost! You will find a short introduction to me and my scrambler in the 'People pics' section.
I have a bundle of questions, and I am sure most will be pretty basic or even daft, so bear with me, I will start with two that are bugging me and slowing progress:
Sparkplug length:
I have a 1971 350 Scrambler and am a little perplexed by how high in the threads the sparkplug (Standard = B7HS) seems to lie, so deep that it appears to be totally covered by the threads. This was noted in a post by bikester250 back in Jan 2019, but no-one seemed to be forthcoming with any thoughts on this, so I wondered if I could ask again. Is this normal, Is it a problem and what is best way forward.
I have the additional problem that this head has a rather industrial thread-insert that has a 2.5mm collar on top, which therefore lifts the plug further still up the threads.
Although the engine runs OK, this doesn't look right to me and I am trying to work whether to ignore, use a different plug or try something different. As bikester250 pointed out, using a projected plug (B7PHS) will go some way to correct this, but with the insert, it will still be pretty low. Going to a 3/4in reach plug (B7ES) is a big jump and I worry will be too long, unless I used a washer above the insert, to raise the plug a couple of mm more. This could be a loose washer, or if I was confident of how it would work, I could solder a copper washer onto the top of the brass insert, making it permanent, but of course would need to do this before returning it (hopefully permanently) into the head. Any thoughts on any of these questions would be appreciated. What is the best way forward?
Removing the Bevel tube from head:
I realise this question will be pretty basic and I am sure a little gentle research would answer the question, but as I have your ear... I have the head off and want to remove the bevel tube to replace the failed gasket between it and the head. The Haynes manual seems to suggest it will just 'come off' leaving the bevel shaft it place, but if so, it needs a knack or method I don't have. Never been good at puzzles, but it looks to me like the bevel shaft/bearing is going to have to come out to allow me to remove the tube. So first, is there a way of removing the tube without the shaft? If not and the shaft has to be removed first, what is the best way to get it out. Manual suggests tapping it out from above, which I can understand, but never like pushing/hammering when the bearing is taking the pressure. What is the safest way to remove it?
Thanks in advance
eib