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Old 06-16-2011, 09:27 AM   #1
LC Garage OP
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Vintage Dirt Racing on a 350 Honda Twin

I have been posting a little on Oregon Coast's Baja thread regarding some of my own efforts and adventures with vintage SL350's and thought it was time to get off of OC's thread and throw my own out there.

My current vintage ride is a 1972 SL350 that I had owned in 1985 and prepped and raced in a few grand prixs (they were somewhat like the current motard races and very popular back then). Anyway, I had ridden this bike a few times and then sold to a friend who has had it in his barn for 26 years and recently gifted it to me with the condition that I vintage race it. Done deal! The initial picture is of the bike after being first brought back home.

When first built, funds were limited and bought the original bike from the local Honda dealer where I worked for $50. Out of the scrap heap we found a set of '73 CR250 forks and front wheel (35 mm and fit SL350 triple clamps), we lengthened the swing arm one inch, put a good set of shocks on also cut off any thing un-necessary and drilled a number of holes here and there, ostensibly for lightening the bike, but probably saved 1 pound off of the original 300!

The local Honda rep at the time was Adrienne Browning (sp?) and when he found out what I was working on, volunteered that he had a brand new SL350 motor in his garage and claimed it was a spare motor from one of the official Honda Baja efforts. I have no idea if that is true but quickly coughed up the $100. price tag and brought it home.

The top end was pulled off and a Pow Roll 400 kit installed, and then added TT pipes and later on a pair of RD350 carbs (they never really ran quite right either). After a few races and several trail rides, I had the money for a new RM465 and sold the bike to my friend.

So 26 years later I have the bike back again and decided it would be a good idea to race in the upcoming vintage scrambles at PIR (6/25/11). It took about an hour of carb & points cleaning to get it running and surprisingly did not smoke. Because of family obligations I waited until last week to get started and now am regretting that I didn't start sooner, there is a lot to do!

The bike is relatively intact from when originally built, but the TT pipes are gone and now have scrambler pipes. There are a few other subtle differences and I am unsure if it is even the same motor I once built, I won't know for sure until the motor is torn down and checked for the Pow Roll piston kit.

In the last week, I have cleaned and serviced the steering head bearings, serviced the front forks and changed over to fork gaiters, and last night changed the carbs to a set that Oregon Coast (OC) generously gave me.

Still to do; grease wheel bearings, new tires, new chain, service rear shocks and swing arm, adjust valves and cam chain, new points, synch carbs and many other small tasks. My biggest worry at this point is that I did not get all new cables and am running out of time, I have a new front brake cable ordered and OC is donating a new throttle cable but will just have to make do with the original clutch and rear brake cables.

Let me know if you are interested and I'll keep posting some updates and pictures. I've included a link to Smug Mug so that you can look at the original and current pictures of the bike and will update as time allows. http://lastchancegarage.smugmug.com/Motorcycles/SL350-Retrospective/16474080_FMjKs#1239759180_XeUwZ
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Old 06-16-2011, 06:43 PM   #2
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Cool!
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Old 06-17-2011, 09:30 AM   #3
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Great Stuff!!

Now don't make that thing run too good, I don't want you to smoke me at PIR on the 25th!

BTW, I probably have spare used brake and clutch cables laying around that you can have as back-ups..I'll bring them along.

I can't wait to see that bike racing again after all of these years. Always sad when an SL is just sitting, rotting away in a barn.
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Old 06-17-2011, 02:34 PM   #4
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Carbs & Stuff

Have been making good progress on the SL, carbs worked great, pulled apart to check and found that one bowl had pinholes but otherwise all in great shape. I also found out that CV carbs don’t exactly fit the SL frame, had to dimple the frame for the choke shafts and also some creative engineering on the intake tubes. The rubber intake boots (LH especially) was starting to tear under the strain of havng been mounted in a bind. I dimpled the frame on each side and then before installing sealed the intake boots with black silicone. Then when I started to tighten the clamps, they were deformed from before and started to collapse. So after thinking about it all day yesterday, when I got home I cut and rolled some little exterior tin sleeves for each boot, so that when the clamp is tightened it spreads the load and tightens evenly, carbs are now secured and even look to be pretty close in synch. Tomorrow I will finish up the front wheel bearings and mount new tire, then move to the actual tune up and get it running, after that I will attack the rear wheel & tire, swing arm and shocks. Whew!!
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Old 06-19-2011, 09:00 AM   #5
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Progress

Saturday made good progress, but hit a few snags. Started the tune up and began by adjusting the cam chain and then the lh valves, when I went to do the rh valves the tappet cover screw would not budge and I am embarrassed to say I did not have an impact driver (I do now!). Since I was waiting to pick up inner tubes and chain from my friend Brian (Wide Open Motosports) and he was not coming home until 5, decided to go ahead and start breaking down the wheels and tires.

Started on the front and as soon as I pulled the brake panel off, one of the brake shoe liners fell off in my hand ~ shi*! Had never see a bonded liner just fall off like that, so now I will need to rush order some shoes first thing tomorrow. The tire had not been off for a few decades and was pretty well stuck, so I remembered I had bought an antique iron bead breaker a few years ago at an auction and decided to give it a try. What do you know, it worked perfect.

Moved to the donor bike and pulled the rear wheel. As I was pulling it apart, I was thinking about what bits and pieces I could use now or as spares and as the brake panel separated from the wheel, one of the brake lininers fell off in my hand ~ double shi*! So I again used my handy dandy bead breaker and dismounted that tire as I needed the rear wheel to replace the one on the race bike as it has 4 broken spokes. After examining the wheel more closely, I came to the conclusion that maybe I better just try salvging the spokes and fixing the wheel I have.

So now it is close to 5 and I am going to head back to town, I pull the chain from the race bike for a sample and off I go in my old beater Volvo commuter car. Stopped at Napa, bought the impact driver and went to Brian's to pick up my parts. I get to Brian's and since his Blazer "Stinky"
is not in the driveway, thought that since I was pretty greasy and dirty that I would just wait til he got home and not go in the house and bother the family. I was a little tired, so kind of dozed off. I woke up and a police car was driving by looking at me. Hmmm, not good. He turned around, pulled up behind me and came to my window. He wanted to know who I was and what I was doing. I explained my business and he was cool, just said they had been having some issues in the neighborhood and my presence (greasy & dirty, sleeping in an old beater) had made someone nervous!

At this point Brian was late and I could not get him on the phone, so decided to head home. I got about a mile from home and the car quit! As I am working on the car, Brian calls to tell me that he is now home and it was his wife who called the police cause she did not recognize my old car! He thought it was pretty funny but at the moment I was failing to see the humor! I finally figured out the problem on the car, hot wired the fuel pump and make it home. What a day!

Today I'm planning to continue the tune up and get as far as I can, want to hear the bike run today if at all possible. Tomorrow I plan to do a next day air order on the brake shoes and anythng else I have to have. Stay tuned. More pics on smug mug. I would post multiple pictures on each of these posts, but so far am only able to do one pic at a time, any advice?
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Old 06-20-2011, 10:29 AM   #6
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Brakes, tune up and other fun things....

Even though there was a lot to get done on the bike, yesterday being fathers day I decided to put family stuff on the front burner and in the morning we went to town, bought the wife a Rav 4 so that I can now drive her old Highlander and get rid of the cursed Volvo.

In the afternoon the youngest daughter came over for pizza and we decided to break out the dirt bikes and ride. My wife rode a little bit but the daughter and I tore it up for quite a while, I finally went in the shop and worked on the SL350 while the daughter continued riding around the property. It was a great day, we all had fun and still finished the tune up. I can now focus on finishing the chassis, getting it rideable in a day or so and work the bugs out. Time is tight but we will get it done.

Here is a picture of the front wheel from race bike and rear wheel from donor bike, note the brake linings have fallen off both. A rush order has been placed for brake shoes and OC is also bringing some spares.



Here is a picture of the motor during the tune up process (now completed), note the tin sleeves over intake boots that have been sealed with silicone. Previous owner had installed the CV carbs at an angle, deforming the boots and slightly tearing the LH boot. After I dimpled the frame for choke shaft clearance and got the spare set of carbs from OC sitting in the boots straight, each time I tried to tighten the clamps the boots would deform and collapse. The tin sleeves now distribute the clamping force more equally and the carbs are now straight and tight.

I did end up having to drill out the screw that holds the RH tappet adjustment cover on, the impact driver just rounded out the slots, so I got out the mighty makita out and killed the screw. When I have time I will easy-out the bad screw and reinstall the cover.

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Old 12-04-2012, 10:21 AM   #7
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Thanks LC, might try those on the next one. I'll be keeping an eye on this thread, those SL350s are super cool!
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Old 12-07-2012, 04:34 PM   #8
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Finally all caught up with this thread, good read.

Is anyone aware of a good cheap coil option? My wires are crusty and plug caps are a loose fit. I went to remove the plug wires, but they are molded into the coils. I've got a set of airhead Bosch coils, not sure of they are a match ohms wise. Any help appreciated.

How's that SL motor coming?
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Old 12-16-2012, 05:59 PM   #9
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Priorities

This post is titled priorities, because it always seems like I'm off on some tangent that doesn't relate to vintage dirt racing on a 350 Honda Twin. Two weeks ago, my daughter in the Air Force announced she was getting married during her Christmas leave, to her fiance....in Houston. Yikes. So with three weeks notice we are gearing up to fly to Texas and helping in any way possible to set up the wedding and make it all work out, and of course we will. As is typical, I'm juggling my duties as a parent, grandparent ( I have 4 grand-kids by my two other children) and of course a full time job, a shop with a bike being prepped for the 2013 MK1, my TTR250 prep for the D100 and of course the old SL350 that doesn't get half the attention I'd like to lavish upon it. Thus the title priorities, I do know how blessed I am, just saying that there is a lot competition for every waking hour.

So this weekend (my last chance to do anything in the shop for a few weeks) I had three projects to prioritze; First was our recently purchased older Motor Home (this will be our "adventure vehicle" until one of us wins the lottery and we can buy a proper UniMog!), with a leaky roof and in temporary dry storage so this can be addressed. Second is the TTR250 because if I don't start riding pretty darn soon, I won't be worth a lick when it is time to race. In addition to the D100 on April 6, I've told Luke I'd like to hit at least one, maybe two OMRA events prior to the D100. Third was to try and squeeze some time in on the SL350, and to do all of these things while also working in going to a basketball game my oldest grandson was playing in. Whew!

Working on the Motor Home roof, got one coat on all seams, need to do two more before we pull it out of storage;



TTR250 thread can be found here;

http://advrider.com/forums/showthrea...=654212&page=2

This is the last photo of the day on this project, good progress being made;



And a shot of the SL350 frame, with another possible fuel tank picked up off of ebay, I kind of like this one, but it will take some massaging to get it to fit;



That's all for now, take care everyone!
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Old 12-18-2012, 06:48 PM   #10
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Oooh, very nice! Is that an MT250 tank Rick? It looks great on the SL.

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Old 02-02-2013, 09:25 PM   #11
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Top End Assembly - Phase 1

At long last I'm back on the old twin, all the other projects are doing well:

TTR is finished and rideable again;

http://advrider.com/forums/showthrea...=654212&page=2

Luke's MK1 bike is coming right along;

http://www.advrider.com/forums/showt...823952&page=21

And the new (1986) race support vehicle, aka "Minnie Winnie" is progressing steadily, although I'm pretty sure we're going to have the pull the furnace to repair, but that is another story. Anyhow, with all these projects slowly coming together and the majority of my honey-do's somewhat under control, I had a whole day to devote just to the old SL350.

This morning;


Decided to use the tensioner arm on the left for the Polyamide sprocket and wheel upgrade, as the right hand one was in pretty good shape and can be used again on a non performance application;


Drilling out original rivet that holds tensioner wheel in place;


The center bushing from the original wheel must be used in the new wheel, note that the oil passages need to be aligned for proper lubrication of the needle bearing;


Magic marker used to mark where oil passages line up;


Swedged the rivet with tapered punch and then finished off with a brass drift;


Cylinder cleaned and ready for honing;


Cross hatch;


Ring kit came from Greece and are universal 68mm, which require a lot of filing to work in 67mm bores. Because the quality of the rings is completely unknown, I opted for a pretty generous ring end gap. Starting from the top ring at .016, then the second ring at .12 and the oil ring at .010. The rings have no markings of any kind and the compression rings were completely symetrical, so without any position indicators, I just have to hope that they are going to work. Note: these were the ONLY rings I could find that were even close to fitting the antique PowRoll big bore kit.


All parts laid out: cleaned, honed, filed, etc. and ready for assembly (the long slender black lines to the left of the rings are the inner springs for the oil control rings, those had to be shortened as well);


Heat gun was used to warm pistons for installation of wrist pins;


First piston on, I quickly realized it would be a good idea to install the inner wrist pin clips before putting the pistons on the rods;


Pistons and rings on and rebuilt tensioner in place, ready for cylinder;


Note to self; no more multi-cylinder ring installations without proper ring compressors. Doing this alone and without the right tools was no fun and was lucky no rings were broken. Whew!


Had figured on getting further then this today, but couldn't quit untiI the trick LameCo head was set in place, just to see how it looked. Yeah Baby!!!


One more shop session should have the motor buttoned up and then it will be on to the chassis. My old crew chief Randy has volunteered (insisted actually) to paint the frame, fuel tank and side covers, and if his past work is any indicator, it should look pretty sharp. Here is the my old 750 Norton that Randy helped build in 1975, he did all the paint and trim work on it;



Stay tuned!
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LC Garage screwed with this post 02-09-2013 at 12:09 PM
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Old 02-03-2013, 06:20 AM   #12
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Nice to see you're getting a chance to work on your 350.
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Old 02-03-2013, 09:23 PM   #13
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Originally Posted by LC Garage View Post
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Stay tuned!
Nice progress and a great shot
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Old 02-04-2013, 07:45 PM   #14
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Rick,

The SL350 motor looks great. Glad we could help. We'll miss you at the Mexican 1000 this year. Plan on being there next year!
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Old 02-05-2013, 08:10 AM   #15
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Rick,

Plan on being there next year!
Most definitely!
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