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  • Rank:Bronze Member
  • Posts:25
  • From:USA

Date Posted:08/10/2018 4:07 PMCopy HTML

A question about an 1975 xl175 header bolt/nut torque and spinning in engine case

Can anyone tell me the manual spec/or suggest a ftlb torque wrench setting for 1975 xl175 exhaust bolt nuts?I have looked all over the web and cant find it anywhere; in any online manuels.

I did find one(torque spec for exhaust nuts) but for a XL125; it was 11 or 12ftlbs I think? This was a few weeks ago I did this.

So took exhaust of to patch/paint; had air leak issue when put back together.Found out about copper crush gasket/washer which I didnt see/notice as it didnt fall out and was coverd in carbon.

So I orderd 2 copper crush washer/gasket for engine/exhaust connection.So I set out to install crush washer to seal up the exhaust leak there.

Anyway as I got close to the I think it was12ftlb? And since the 175 is bigger than the 125; I was expecting to maybe go a couple numbers/ftlb more depending on how everything 'felt'/went with the 11-12 ftlbs.(The only torque spec I found for a XL125 ).

However I never got to make that call because one of the studs that comes out of engine (and you put nut on to mate exhaust pipe to engine) started to turn slightly; about a quarter of a turn.

*side question(should i have used some type of grease/antisieze on these header nuts?)  As far as bolt issue;I would just like to know if that definatley would mean a problem,or it might be ok,and how to find out ,and or proceed about the stud spinning slightly.

I hope this hasnt made things worse.
I immediatley stopped.

**(NOTE)Id like to know this issue addressed before proceeding.I.E. that cush washer is crushed/sealed; and that I have no leak at engine/exhaust connection.

 i.e. also possibly has idle/choke issues/vacumn leak elsewhere,since had to pull carb and clean ,and not running right since.)

So now Im not sure how to proceed from this point im at.

So Im thinking if at least if I could get a sugg. ftlb range;

and any sugg/idea's about that exhaust/engine side bolt starting to turn 'stud' inside engine case, side of exhaust mount area,I might know what to do to proceed.

**If i take off nuts /header to see if copper gasket is crushed; then tech. im supposed to use a new one (copper crushwasher/gasket) to remount the exhaust header.Ihave 1 good one still.(I bought 2 offline just in case)

But if I take pipe off to check if washer is crushed,im back where i started,not knowing what torque,and theres the issue of the header stud/bolt that spun 1/4 turn.

Except I guess if washer was/is crushed I would know 'more' ftlb isnt needed when i put the next/last crush washer on that i just like to know for sure than to be winging on very low fixed income.

(i.e. if I dont/wont know if it is fully crushed.I cant rule it out as poss. cause of air leak...improper idle/choke running problem. etc)

NOTE:it doesnt 'seem' to me the gasket is crushed ,the nuts are not all the way down/snug (there are some threads still showing on bolt/stud whatever) and I seem to remember( 97% sure) the nuts were  tightend all the way down/no threads visible when I took it off to paint etc.
I can get a pic later ,I have pulled calf muscle and live upstairs ,so can get pic when i 'have' to go downstairs.

I am slowly getting there by using /reading this site thanks alot everyone,I hope to contribute as i learn/go as well.I Have another question but it deals with electrical so will keep it seperate and wait till this hopefully gets comments/suggestions.
Thanks again to everybody.

XLKirk #1
  • Rank:Gold Member
  • Posts:175
  • From:USA

Re:A question about an 1975 xl175 header bolt/nut torque and spinning in engine case

Date Posted:08/22/2018 4:01 PMCopy HTML

Hey there, pulled out my Clymers manual and they don't make a specific mention of torque settings for the the exhaust bolts, however, there are specs for the cylinder covers and crancase bolts. I'm asuming you would want to use these since they relate to items bolted into the cylinder and crankcase. 6mm bolts are set at 6-10 ft. lbs. and 8mm bolts are set to 15-20. The Exhaust flange nuts are 8mm so I would use that spec. 

The exhaust pipe stud turn issue was probably created when you removed the pipe the first time. It's fairly common that the stud loosens a little as the nut is broken free. I wouldn't worry about it, just make sure the stud is set at the bottom of it's travel when you tighten the nut to the torque spec. This will eliminate any possible errors in the proper torque setting being attained. 

I wasn't sure about your experience so I hope the following doesn't insult you, you may already know this? Your really after "does the system leak". Having the split rings square and uniformly contacting the exhaust flange / collar and also flush - uniform against the copper gasket is critical for a good seal when the tightening the nuts. Try to bring the nuts up uniformly - snug one - then the other. Don't bring one nut all the way down to spec and then tighten the other from a loose condition. I always use a high temp anti sieze on the nuts or bolts when installing on a motor. First it helps to lubricate for a more accurate torque setting and makes taking them back off much easier! I will also take the time to steel wool the threads to clean up any imperfections prior to install. Just understand that if you do this, that you don't need to rub very hard and damage the thread - your just cleaning them up. AND always clean off any debris left on the bolt or nut before install.

As far as your idle / mixture issue. Did it run good before you took the carb apart and cleaned it? My guess is there is a setting issue with the carb or you may have created a vacuum leak in the intake manifold during remove and replace. The intake manifolds are rubber and if it's the original......... like mine was.... it took a set over the years and simply does not fit the carb flange well anymore. I dinked with the carb FOREVER! only to finally realize that air was leaking between the carb flange and the intake manifold. I even tried a heavy duty hose clamp and that improved the condition, but did not solve the problem. As far the carb settings go - get your self a good Clymers repair manual (if you don't already have one) and revisit all the settings. Mine has helped me a lot. 

Good luck!

Go soothingly on the grease mud ... as there lies the skid demon! ...

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