Maintainer: Alan Fleming (alanf@dorje.com)
Version: 1.9
Date: 11/21/98

1) What engine did Yamaha put in the SRX600? Is it the same engine that was in the SR-500 or the XTs?

James Montebello:
Roughly the same engine as that in the XT600. The engine is a derivation of the SR engine, but I doubt it shares many parts with it. Later XT600 engines have different (stronger) cases and (tad da!) an electric starter.

Andy Scheen:
It's quite diferent,the SRX engine is a 4 valve twin carb twin exhaust port design 95x84 bore and stroke,dry sump aircooled w/a balance shaft and five speed gear box.It's virtually identical to the TT 600 engine.The TT has a diferent ignition flwwheel and the swingarm pivot is incorporated into the rear engine mount.

Stefan Karsch:
Yamaha took the motor of the '86 XT600, but with a bit longer 5-th gear.

Mark Covert:
Right before the srx600 was released in the states, I was working at Kenny Roberts' Yamaha in Modesto, CA. KR had one shipped over from Japan (?) and it had a 608cc motor. It was bone stock and that was the size engraved on the side of the cases. The US model had a 598cc motor (within a cc or two). Just thought you might be interested in that.

2) Are other parts on the bike from other bikes? (forks, swing arm, instruments, etc?)

James Montebello:
Forks are very similar (if not identical) with the parts used on the FZ600, FJ600 and Radian, as are the front brakes.

Andy Scheen:
I'm not really sure but I know the rear wheel is quite similar to a RZ 350 you can use the sprockets and they look virtually identical.

Stefan Karsch:
I think the fork is from the RD350, the rear shock on early models are from the XJ900.

3) What are the most common modifcations for the street? Are there any fork, brake and/or wheels that are bolt on options? Are there any companies in the US or elsewhere that sell hop-ups, additions, etc?

James Montebello:
FZR front ends go on without a lot of effort. FZ swingarms can be modified to work (either weld up twin-shock mounts, or fabricate a mono-shock mount). The stock swingarm will accept a very wide (like 5") wheel. A pipe and an jet kit are very common, and help a lot. Most of the pipes are Supertrapp types. White Bros. is a source of parts and info. Pistons kits, cams, oil cooler kits, shocks, etc. are all available for the bike. Noleen with sell you super-trick Ohlins shocks for it (as long as you're not in a hurry :-). Sudco has Mikuni CR Special (smoothbore round-slide) carbs in various sizes for the bike. 31-33mm seem to be acceptable for street use with mildly tuned motors.

Andy Scheen:
The best street mods seem to be new carbs and a good pipe. This makes a world of diference. The stock carbs suck and nobody makes jets for them tuning is impossible. Sudco ofers real nice Keihin cr specials (round slides) in 33mm and 35 mm sizes imho 35's are to big unless you have a really radical motor. I think White Bros. has a complete pipe still and Supertrapp sells a slip on. White Bros. also has pistons, cams, a 640 kit, etc. Megacycle has cams as well. Muzzy made a pipe but I don't know if it's available anymore. I don't know of any "bolt on" wheels or forks but they can be changed fairly easily. FZ 600 swingarm almost fits right in but requires a little grinding and shiming as well as needing rear shock mounts welded on. A FZR 400 front end will go on pretty easy but the stearing stem is a little diferent. My bike has a Hurricane front end and this required line boring the clamps and making new spacers. Mono shock conversion is pretty easy using a FZ600 swingarm and RZ350 shock, for someone who is experienced with this kind of work.

Stefan Karsch:
Does the US-Model have an oil cooler? The German one has no oil cooler but the japanese model has one. So installing one is a useful modification.

Johan Drost:
Interesting article from James M. About the power drop at high rpm: I had the same problem, tried another exhaust (Super trapp), Dynojet kit, K&N filters, shortening spark plug cable etc., nothing helped. After that I put my SRX on a Dynojet test stand, it came up to 28 bhp at approx. 5000 rpm, then it dropped to almost 0. After having classified it as an electrical problem the first thing we tried was a what I did with my Yamaha moped (50 cc) 15 years ago: disconnecting the side stand switch. Re-run on the test stand: 43 bhp at 6500 rpm, with a theoretical top speed of 122 mph, which is quit good for a more or less standard (Super trapp/ Dynojet) SRX. That same day another SRX owner came by with the same problem, this was also solved by disconnecting the side stand switch, it appears to be a typical Yamaha/SRX problem.

DJMoran:
When I had the suspension redone on my bike, I had Race Tech emulators installed along with the PS fork springs. Sorry I don't know the fork oil level or type as I left that to the professionals. What I can report is that the front end is FANTASTIC! Little or no brake dive, compliant, planted, and very smooth. I also suggest tapered roller steering head bearing to help the front end loose that clicking into place sensation after 40K.

Thomas Allen:
Hi there,I just finished putting the engine back together in my SRX6 after having it sitting in a box for the last five years and I put it back together the way it should be. I sent the head off to have it polished and ported at Kausa Motors in Toronto, they also ground the valves and installed my titanium valve springs that I got from White Brothers. They also honed out my cylinder just a wee bit so I have to use a 1 mm larger piston. I put on a Lockhart oil cooler, put in a WB1150 track cam, Wiseco 11-1 piston (1 mm bigger than stock) and I installed a White Brothers pipe with a Super Trapp slip on.
Now when it came to the carbs I called up another guy who I knew did his own SRX in Toronto and he kept the stock carbs and drilled them out and sent me a copy of what he did. So I was torn, do I need new carbs for $500 CAN. or do I modify them?? Well I used the Dynajet kit and K & N filtres and figured if it didn't work so well I could always buy the new carbs, but from what the other guy in Toronto told me I probably would not want them. I made the right choice, the fltres fit (a bit snug maybe but they work) and as for my carbs, perfect, no need to waste money. After five years of sitting in my shop my SRx came to life with no more than 3 kicks and it runs great with 18 (count 'em!) disks on the Super Trapp muffler. My bike runs great, just a couple of kicks in the a.m and it starts, no choke unless the temp out side is colder than 10 degress celcius and when you use the choke you turn it off right away.
I strongly recomend that if anyone is serious..and i mean serious about doing the engine on this bike that they have someone who knows there stuff to do the head, it doesn't cost much and it makes a lot of sense. The Yamaha carbs work great and they do NOT need to be replaced, I don't know about you but $500 is a lot of bucks to spend when you really do not need too, besides that is half the money I need now to do the rear suspension ( yep..ohlins ) and put on a top steering head damper.
Tell you one thing, I was using a shop manual from an XT600 to do my hop up and that was a mistake, it never showed that I needed a cylinder gasket, good thing I called the guys at Yamaha about that one.
So anyhow my bike came back to life at 23,990 kms after sitting for 5 years and runs better than I ever hoped it would,I'll have this one until I die...no doubt about that.

Mark Sievers:
The FZR swingarm modification is a real chore, although the FZR triple-tree swap is fairly straighforward. Tapered roller bearings for the SRX will fit the FZR600/400 steering stem, although the lower bearing was very, very tight on mine. A spacer is needed below the lower bearing; I milled a 5 mm spacer which worked fine, and I heard someone else say that they used a .25 inch spacer. I also used all FZR hardware, including the top nut, adjuster nuts, etc. I also drilled and tapped the lower clamp on each side of the stearing stem for mounting a steering damper and an RZ350 cafe fairing frame. The SRX ignition switch fits in the FZR top clamp, too. I mounted the brake-lines to the lower clamp using the mounting clamp from an '89-'90 FZR1000 (it also has a horn mounting tab, which is neater than the stock SRX horn mount, I think). Oh yes, I had already converted the 1-into-2 brake lines to 2 lines from the master cylinder to the calipers -- very simple. Also, plan to mount a set of after-market clip-ons below the upper clamp, because there will not be enough fork tube above the clamp to mount the stock clip-ons. That's it, for the fromt. The swingarm modification must be done by a good machinist!
It is fairly complicated and requires some creativity for manufacturing the upper shock mount, assuming that you want to use the single shock. (My experience is with an FZ600 swingarm and FZR600 wheel, but there should be little if any difference in the procedure for mounting the FZR400 swingarm.) The SRX pivot bolt fit the FZ swingarm bearings and spindle, but the swingarm is too wide at the pivot and must be milled. Before doing this, compare the position of the SRX wheel in it's swingarm to the position of the FZR wheel in it's swingarm; you will probably find that one is offset relative to the other, and you may be able to compensate a bit when fitting the swingarm to the frame -- otherwise you may need to modify shims to get the rear wheel in line with the fromt. The front linkage mount is a fairly simple fabrication job and fits nicely at a frame crossover brace below the transmission. The upper shock mount fits nowhere easily, and the configuration of the mounting bracket may depend on the length of the shock that you wish to use and will be very important in determining the leverage ratio of the linkage. At this point I have to bail out and say that I know much too little about linkages, leverage ratios, etc. to be giving you any advice whatsoever, except that you need the help of a good shock man as well as a good machinist. I ordered a custom shock from Works Performance, and they helped me out a bit by telling me how to measure the leverage ratio and whether or not it would actually work. I believe that I got lucky (or, rather, my machinist's judgement was excellent) because they said that mine would work OK for the street, but not great for the race-track, and I'm no racer! I was able to keep the top of the SRX airbox, so I'll be able to mount the battery in the stock position, if I ever want to use it. Of course, the bottom of the airbox had to be cut off to make room for the upper shock mount. I also had to use a 16 tooth countershaft sprocket because the FZ swingarm is thicker at the pivot than that of the SRX; you may not have this problem with the FZR swingarm.

AtheT:
SRX 600s also respond well to carbs from gpx250 kawasakis The 250 Ninja, as it is called here in the states has 30 or 32mm carbs depending on the year- and they will plug onto the stock yamaha manifold with minimal work. Reliable, good idle, and plenty of power...

Stephen Harrison:
My bike is a 1992 Japanese import, so it comes with 17 wheels, 38mm front forks, a single front disc but with 4 piston brake caliper, mono shock rear end. It runs Bridgestone BT 35S tyres. 110/70 front and 140/70 rear. What made the biggest difference to it was an Over racing exhaust system, just this alone seem to liberate the engine. The only problem is that in fitting it you have to dump the passenger footpegs. The high level carbon fibre can really makes the bike look nice. I then added a K&N filter and a Stage 2 dynojet kit. The bike really does accelerate well, with no hesitation when you snap open the throttle, but as the temperature starts hit the 40 Degree level, I get a little "Hunting" when I am running with a part open throttle at about 4000 RPM. I have some great addresses in the U.K. for companies that do Big Bore kits, tuning parts and even 17inch wheel conversions for SRX's.

4) What about touring on the bike?

Stefan Karsch: For longer tours the bike appears to me uncomfortable. Its just for fun.

Carsten Whimster:
Someone quoted in the SRX FAQ said that touring on the SRX is not great, and while he is right to a certain extent, it is certainly possible.
The greatest difficulty is to get enough cargo space onto this little bike. Soft saddle bags tend to rub against the shocks and/or the wheel! I had the above mentioned bags :) and a tank bag, in addition to some stuff strapped onto the back seat. If anyone ever finds soft luggage to fit this bike well, I would love to hear about it. I rode mine 39000 km from Toronto, Ontario through Vancouver, BC and LA, California and back. When it was windy, it was a pain, but when it wasn't, I could keep cruising speeds around 110-130 km/hr no problem. All with no fairing.
The first week my ass was in trouble, but after that I was fine (basically my ass got tougher). In the twisties it is great fun, and on highway 1 in California I managed to leave my friend way behind, on a Ninja 750! It was a long great trip, tough in places, but I never regretted it.
I don't think I could ever redo that trip on a more suitable bike without thinking that I had somehow gone soft :) One good thing is that the wind noise tends to be less than on a fairing fitted bike, even if that does mean more wind in general.

FR11:
I would disagree that the SRX6 is "just for fun", I have done 104,000 Km on my bike which have included riding from Germany to Spain in one day!
It can be done, but you must maintain at least 80mph to take the weight of your arms. The saddle is comparable with other Jap bikes over this sort of distance, and the only draw back to using an SRX6 for this type of "holiday" work is the narrowness of the seat and fuel tank, which restrict the amount of luggage that can safely be carried.

5) Any must-have accessories?

Andy Scheen:
A good carb and pipe will make a world of diference.

Johan Drost:
Exhaust system: in Europe BSM Exhaust Systems sells a stainless steel pipe which runs just below the buddy seat, good looks, nice sound, good performance. Strange jet in second stage carb: you will also find these strange things in Harley's, although most Harley dealers only have the large sizes. When you want to change the jet dimension the best solution are small drills. When you want to go down, fill the hole with 2 comp epoxy and re-drill. For a street SRX the standard 100 second stage jet works well, in the winter I use a 105 jet instead of a 100, it gives just a little bit extra.

Steve McInally:
Handlebar riser kits for the SRX are available from V&M Racing, Lower Mill, Shaw Road, Newhey, Rochdale, Lancashire OL16 3SR, UK.
tel 01706 840066, fax 01706 882437 (no web info). I've just ordered a kit comprising adaptor plates, Renthal bars, Goodrich brake hose, bits and bobs. Expensive mind you, the kit cost the best part of #200-00 to have delivered to my front door. Also, Mitsui Yamaha here in the UK will supply the workshop manual free of charge. The catch? It's on microfiche. If anybody's interested I could supply Yamaha's UK address.

6) What magazine articles have been done on the bike?

James Montebello:
_Cycle_ did a test of the European SRX (608cc v. 585cc, oil cooler) in early '86 (Feb?). A sidebar appeared as part of a test of the Suzuki Savage (Aug '86). _Motorcyclist_ did a pair of hop-up articles, one in December of '86 or '87, another about a year later.

Don Workman:
That "Cycle World" did a complete test on the SRX-6 in the July '86 issue. It is a complete road test with quarter-mile times, etc, and more complete than the Cycle Feb '86 "High Country Safari" article. A red model appears on the Cycle World cover. Another Cycle World article is a "riding impression" in the Dec '85 issue, with a silver SRX being tested by current editor David Edwards.

7) What is the going price for a good condition SRX-6?

Alan Fleming:
This is an anti-answer. The value of bikes if so heavily relativistic that the price in one area of the country for a given bike has no bearing on the price for the same bike in another part of the country.
Ultimately, you need to determine local value by checking the classified section of your local newspaper, check with local shop and ask around.

8) What resources are available on the net?

Alan Fleming: The THUMPER web page (http://www.thumperpage.com/index.html) is an excellant resource for meeting other Thumper owners. Likewise, the THUMPER mailing list (listproc@dorje.com) is home to many SRX owners. Also, anyone interested in roadracing their Thumper should subscribe to the roadracing mailing list (listproc@micapeak.com).

Contributors:

James Montebello (jamesm@calweb.com)
Andy Scheen (scheen@ix.netcom.com)
Stefan Karsch (Karsch@rz.RWTH-Aachen.DE)
Carsten Whimster (bcrwhims@uwaterloo.ca)
FR11 (R.J.Farnish@greenwich.ac.uk)
Thomas Allen (Tom.Allen@city.saskatoon.sk.ca)
Johan Drost (johan.drost@tip.nl)
Mark Sievers (marks@sun.sws.uiuc.edu)
Thomas Allen (Tom.Allen@city.saskatoon.sk.ca)
DJMoran (BOZOPNW@aol.com)
Mark Covert (cove@inreach.com)
Steve McInally (ucaisgm@ucl.ac.uk)
AtheT
Stephen Harrison (harrisons@ksamail.com)
Alan Fleming (alanf@dorje.com)

Think Peace.
- Alan (alanf@dorje.com)
http://www.dorje.com:8080/~alanf
KotBBBB (1988 GSXR1100J) RaceBike (FT500)
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