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-   -   Honda 400 engine advice please (Honda Falcon) (http://www.horizonsunlimited.com/hubb/honda-tech/honda-400-engine-advice-please-49064)

Sheonagh 17 Mar 2010 17:50

Honda 400 engine advice please (Honda Falcon)
Currently on a couple of Honda Falcon NX400's (Think NX650 format with XR400 engine, made in Brazil) doing a long Tour (Central America, Far east and keep heading west...) and doing a little routine and other maintenance in Los Angeles.... My Questions
Who in that area might have a lot of experience with XR400 engines...?
When I took the spark plug out of one it was very stiff and brought some alloy with it, the new one has gone in and tightened down but I wonder if I should pull the head off and helicoil the plug thread?
  • What would cause a plug to seize / damage threads. Possible overheating?
  • should I leave well alone or recut the thread/ helicoil? There is like 11 turns of the thread and perhaps/ the first 4 may be a little dodgy now, is it possible it might spit its plug out if I leave it any experience? Is There enough metal to put in an insert?
  • removing rocker cover... it is likely that I overtightened the small bolts last time I had it apart. If I encounter damaged threads is there enough metal to helicoil these..... any experience
  • How long do these engines last ( big ends etc) they have been regularly serviced. Fed oil, had timing chains replaced. Are not obviously using oil between services..... have now done 56000km (35000 miles) any experience?
Any advice would be very gratefully received.....
Sheonagh (and Pat) aka 'Dusty old bags'
PS anyone got a spare crate near here ?

Philip Reed 12 Feb 2013 04:49

I am interested in buying a used Falcon 2008 with 26,000 km on it, here in Costa Rica. Everything here costs twice as much as anywhere else so it will cost almost $7000 after I pay it off with interest, my question is: is this bike something that is worth investing in can be worked on and kept like new over the long haul.Anyone have any input? My other alternatives are to buy a much older bike, or a much cheaper chinese 400, or pay a lot more for a newer one.

mark manley 12 Feb 2013 06:14

Hi Sheonagh,
Spark plug thread excepted I hope all is well with Pat and yourself and that your trip is going well.
Your problem may have been caused by not copper based greasing the thread before screwing the plug in, use a small amount each time it goes in to avoid this. Depending on how much metal came out with the plug it might be alright until the next time it comes out but it would be wise to get it helicoiled at a convenient point along with the rocker cover threads, it should be no problem for a competant mechanic or engineer to do this.
With the regular mentainance and use it is getting I would have thought your engine should go on for 80-100,000 miles so plenty of life left yet.

Mick O'Malley 12 Feb 2013 08:56


Originally Posted by mark manley
Hi Sheonagh....................Mark

Excellent advice Mark, if a tiny tad late.

Regards, Mick :smartass:

mark manley 12 Feb 2013 18:01


Originally Posted by Mick O'Malley (Post 411392)
Excellent advice Mark, if a tiny tad late.

Regards, Mick :smartass:

Oops! I have actually seen them since then :blushing:

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