Author Topic: SRX 600 misbehaving - thoughts please  (Read 233 times)

srx ijk

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SRX 600 misbehaving - thoughts please
« on: April 25, 2022, 12:52:17 PM »
Hi All
I have an odd problem on my 1JK model, low mileage Yamaha SRX600.
Gets occasional use (say every fortnight) and is usually a good starter and a reliable runner. On the last start up after less than a half mile the bike first started hesitating slightly and then with the bike stationary and the throttle closed, the revs climbed to about 3k + and stayed there until I got it back in gear and limped home. Since it's previous run I had not touched the bike.
I have - taken the carbs off, checked for blockages and air leaks, checked the float level, checked throttle cables, throttle stop, 'choke' valve actuation and replaced all of the petrol with super unleaded (instead of it's usual diet of unleaded) - all to no avail. The air filter is newish and not blocked. Upon restarting the same problem occurred.
Have not come across this problem in the last 50 years of home maintenance motorcycling.
Any ideas?
Glyn

themoudie

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Re: SRX 600 misbehaving - thoughts please
« Reply #1 on: April 25, 2022, 01:28:45 PM »
Aye Glyn, welcome to the esoteric world of the Thumper Club.  ::)

As for the "racing" engine saga query, it sounds as though there is weakening of the air/fuel mixture, though I may be wrong!

Blocked vent from the fuel tank due to corrosion and or blocked drain hose from the rear of the fuel tank to the front of the swing arm pivot.

Perished inlet rubbers between the carbs and the head. The SRX type with a pre-formed curve in them are now difficult to find. But, the XT inlet type do fit and are more readliy available, both as OME and pattern parts. However, they are straight, rather than curved and re-fitting the tank over the carbs can be a pain. A test is to spray WD40, or similar, over the inlet tracts whilst the engine is running and note any change in engine speed or bubbles on the surface of the rubber. The rubber may also have parted from the inner metal supports moulded into the inlet tracts, allowing air to leak between the support and the moulding.

Fowler's of Bristol for OME and eyewatering prices, or Yambits for pattern parts and slightly lower prices. Another possibility is the Japanese 'JAUCE' website, their equivilent to our eBay. However, be prepared to multiply the current price in JYen by approximately 3 times to cover carriage and taxes, both local and import. The quality of used parts is usually good and myself and Ian have both used the service for parts not available over here (UK) for SRX400 3VN monoshock machines.

Perforated diaphragm in the carb causing an air leak. Would suggest a carb refurbishment kit from link: NRP_Carbs

Ian and the Steve's L and H may also be along to add their pennyworth.

I hope this helps as a starting point and suspect that after 50years of motorcycle maintanence you could contribute to our knowledge as well.  ;)

Good health, Bill
« Last Edit: April 26, 2022, 12:11:10 AM by themoudie »

srx ijk

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Re: SRX 600 misbehaving - thoughts please
« Reply #2 on: April 25, 2022, 01:59:27 PM »
Thanks Bill for super prompt reply - will work through your suggestions!

themoudie

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Re: SRX 600 misbehaving - thoughts please
« Reply #3 on: April 26, 2022, 08:57:20 AM »
My pleasure Glyn and I hope that you solve the problem without too much pain!

Good health, Bill

Steve Lake

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Re: SRX 600 misbehaving - thoughts please
« Reply #4 on: May 15, 2022, 11:22:48 AM »
Bill has pretty much covered it all (as usual ;-)), i'd go for the leaky intake rubber/alloy manifolds. i've had several instances of these failing, and not easy to spot, best to remove them and have a close look. i have repaired them with a reasonable degree of success. i thoroughly clean the rubber and the alloy parts with a de-greaser. then use sikaflex 11FC, works for me

srx ijk

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Re: SRX 600 misbehaving - thoughts please
« Reply #5 on: June 03, 2022, 08:32:58 PM »
Just thought an update might be useful - although v. inconclusive

Bike now starting and running well - but not quite sure how/why.....here's what I did;

Carbs off again, carefully inspected inlet rubbers - all OK, reassembled, no change still over-revving at tickover/running badly.
Checking for spark found none - removed cap, no spark, new cap, no spark. So new coil and lead = good spark.
Out for a ride still not 100%, but petrol pouring from float overflow this time - even on run and reserve tap settings!
Carbs off 3rd time - all looked OK but bought new float valve and seat anyway (Wemoto) but didn't fit - turns out 1JK models differ from UK bikes in very slightly different length and diameter - painless refund and website item de-listed. Cleaned and refitted original float valve and seat which worked OK.
Ordered new main vacuum tap (still awaited) but in the interim bypassed tap with direct feed to carb.

Now running fine!

Ian

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Re: SRX 600 misbehaving - thoughts please
« Reply #6 on: June 03, 2022, 10:47:45 PM »
Hello Glyn and welcome to the emporium of supreme excellence.
I'm glad you seem to have got your 1JK sorted. If Bill, Steve H, or SteveL  don't know the answer then the problem may not exist. I tend to tag along, read and digest their fountain of knowledge and enjoy riding my Monoshock.
I have found out, and in sure all the SRXperts will agree is that you need everything spot-on carbwise on these beautiful machines for them to perform anything like. I know SteveL has junked the carbs on at least one of his. May I also add that the latest versions of fuel that is being served up to us doesn't help in the slightest. My 3VN doesn't like E10 or supermarket E5. Keep us up to date with your mods/replacement parts/ etc. It sounds as though you know what you are taking about, so I'm sure you'll be able to add to the encyclopedia on here.
Ian 👍
1 SRX 1 C400X

Steve H

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Re: SRX 600 misbehaving - thoughts please
« Reply #7 on: June 09, 2022, 07:15:59 AM »

Carbs off 3rd time - all looked OK but bought new float valve and seat anyway (Wemoto) but didn't fit - turns out 1JK models differ from UK bikes in very slightly different length and diameter - painless refund and website item de-listed. Cleaned and refitted original float valve and seat which worked OK.
Ordered new main vacuum tap (still awaited) but in the interim bypassed tap with direct feed to carb.


Just checked my parts lists and the 1JK and 1XL (UK) float valves are the same part number. The part number changes from the later 2NX model onwards.

Steve Lake

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Re: SRX 600 misbehaving - thoughts please
« Reply #8 on: July 01, 2022, 02:36:50 PM »
good info SteveH ... thanks