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Discussion Starter #1
I have an issue with my b400 and a supposed valvle that isnt seating properly.
I have a Question
Lets say, youve now bought a new valve, now what? The hole in the head isnt accurate? It has deficiencies in its tolerance. In its seating.So it needs to be ground down to have a new properly angled hole to seat the valve? But then thats metal thats been taken off and not within spec (vs a new head)
In any rebuild ive never had an issue with the head so Im curious how a head is rebuilt with a bad seating head in terms of the valve and head mating properly. Its not like tou can add metal thats been worn away...? Its not like using an oversized piston where the cylinder has worn a bit and you can use an oversized valve. Help me understand the logic please. Cheers
 

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I'll try for short and sweet. You'll need parts wise a new valve, valve guide new valve keepers, check springs or replace. Most importantly this is not a job for the common man. This is highly specialized work. Find a good shop that works doing cyl head repairs. Most valve seats are purchased by shop to exact specs of your job, if it must be replaced, or be ground if enough material remains. Your question is answered by the valve guide replacement which is fitted to your valve on the upper stem perfectly. I come from 26 years of BMW I had a 1981 R100RT. BMW screwed up and installed the exhaust valve seats with a poor choice of material that didn't adequately dissipate heat. Heads went to a speciality BMW machine shop in California. Make sure you use a shop that does motorcycle work daily. I hope this helps. Please ask for clarification if needed. I'm enclosing a couple pics valve guide shown and illustrations are from a 2008 an400 catalog found online


Sent from my LM-V405 using Tapatalk
 

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Discussion Starter #3 (Edited)
This is really good info and thank you for sharing
Im curious what kind of luck I would have by buying a used "complete" torn apart head from a donor engine or buying parts - 4 valves guides springs etc and get it rebuilt. The donor head has 17000miles (though it cant be verified and take sellers word)
And I cant even tell what a good head or bad head would look like

I have to be honest, im not certain there are competent skilled people here. I had a crankshaft/bearing rebuilt or refitted and it came back with some play. Not knowing any better (now I do) I gave it to the installer and 3 months later the engine fell apart with issues in the crankshaft

So I will have to check around but im really nervous woth this. I know their mindset. Having enough experience with shetty mechanics there's a reason why the stigma for people in the industry are considered shet.

If I bring them the parts and have them rebuilt it and it fails they will not take responsibility that they(god forbid) did a bad job. They will throw the blame of the installer and inevitably will have to goto small claims court. Which is what im doing with my last mechanic.

They replaced the crankshaft position sensor. Never called me to authorize repair. Wanted to charge me full price (ckp+stator replacement) but never replaced stator as he said "mine was still good". But wanted full price. Smh.
17 days later after I take the bike my engine dies. Valve is bent supposedly(lose of compression) AND my cvt failed TOGETHER. not possible. Cvt belt was 2 months old. ripping to shreds and I get a belt returned thats not even the b400 size. I compared it to the old belt... Not the same size. No rubber shrapnel in the variator case. Not 1 crumb. No rubber marks on pulleys. Not on anything. The big contra spri g in the clutch has light surface rust. Not a single "whip" mark of the belt strands on it. Guy has No credbility. Never returned my battery till I realized it was missing. Well meet in court as they reopen from c19


Another problem, another garage, who I went to, to repair the engine said the problem is the previous garage make a critical mistake . They took apart the head completely but didnt mark the pieces to which hole/valve. What he said was that each valve is worn slightly different then the other and has it own "wear marks" and just assembling these randomly to a different valve makes slightly different tolerances that will cause issues to have them fit properly.. Is this true? We are talking about doing a precision job after all
 

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Check you have tappet clearance, if ok and you think you can do the work

Remove head, remove the valve if carboned up clean the valve and around the valve seat if it also has build up than drop valve back up, use bearing blue (might call it something else over your way) see if it sets ok, if not, don't lap the valve in with lapping paste (see below).

You could also before removing the head take it for a full throttle blast for as long as possible 30 minutes it will help blast some carbon off, my GS1000 use to run like $hit from riding in town and a blast out in the country once a month helped clear it up :) and my head :)

When I was machining cylinder heads we did work for Suzuki dealer and you can't reface the valves they have a hardened seat face and 80% of the time they didn't seal up passed 75% (vacuum pump to check seating) if you face the valve use loose the hardening coating and it won't last long :-( i used an old valve and refaced it to check the seat was sealing ok.

Good Luck

Greg
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