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Old 12-14-2012, 02:24 PM   #151
FJ_Kevin OP
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Books and other resources...

It has been interesting to look and compare photos of the 465/490 cylinder and porting to the later model engines.
I was thinking that these later motors could provide some guidance for future modifications of the old YZ's.

I mean, why not just copy the porting of the kx500 or cr500?

To see if this was reasonable I spent a little time collecting bore and stroke data from various big bore two strokes. If the stoke is the same as the YZ, then perhaps the port area and timing could be copied over as well... unfortunately, I found no other bike has the exact same stroke.

In any case, here is the table I made that lists the bore and stroke dimensions for the yz465/490 (in all oversizes) and the other big bore two stroke motocrossers. Dimensions are given in metric and english units. The bike with the closest stoke to the YZ at 82mm is the Maico 490 at 83mm.




There is one other interesting point from the table, that is, the standard yz490 piston is equivalent to an 8th oversize for a 465. Can those worn out 465 cylinders be saved by boring to 87mm?

Please let me know if anyone has tried this .





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Old 12-14-2012, 03:02 PM   #152
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Books and other resources...

Books and other resources... continued

So straight forward (if there is such a thing) copying of another makers porting is not so straight forward . So with that I began reading up on two stoke engine theory. There seems to be several good books on the topic, here are a couple of the more popular ones,



The Two-Stroke Tuners Handbook can be downloaded free from a couple of sources (google is your friend). I found the Grahm Bell book to be pretty good too (about $25 on amazon).

If these books dont put you to sleep, try the Eyvind Boyesen patents on porting and reed valves...
http://www.google.com/search?q=Eyvin...w=1189&bih=720


After reading these, the take away for me is that blue printing is about the best I can shoot for with the finite time I have. Yamaha knows quite well what they are doing (certainly more than me) and it would require a great deal of effort and experimentation (access to a dyno) to improve upon the original design.

Also when I look at what a guy like Eric Gorr charges for port work, it's a bargin compared to the time it would take to replicate his know how from scratch.

So my focus was and remains a high quality, reliable rebuild with focus on proper running and jetting. Sometimes I simply forget the bike is too fast for me anyway .

Still, it would be fun to take port area/timing measurements, crank through the equations, and see how the yz design stacks up agaist the recommendations of these books. If I get through all of this I will be sure to post the results here.

Next up will be pistons and the rest of the top end.

First, recall this bike was stolen and then recovered, here is a recent picture after repairing the (minor) damage. The thieves never started it so I am happy to say it still runs great!



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Old 01-15-2013, 09:18 AM   #153
athomerecords25
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FJ,

When you return, if you could look at this thread it would be greatly appreciated: http://www.advrider.com/forums/showt...0#post20489910
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Old 01-16-2013, 04:21 AM   #154
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Well, you could do a lot worse than having a motor with similar specs to a Maico 490. I believe using a standard 490 piston is a common practice in 465 motor builds, which gets you purty close the Maico 490 B/S ratio.

EG loves old school 2 strokes. When I talked to him last year he was getting ready to join Millennium Technologies last November and his prices were getting ready to go up. Still, he can build a 465 to do just about anything you want from the motor.
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Old 01-24-2013, 12:32 PM   #155
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Your bike looks awesome! Did you find any swingarm wear at the shock mount location?

I have a little free play at that location on mine and I'm looking for a way to fix it? Drill and sleeve, Weld and re-drill?
I haven't found a kit anywhere but there probably is not one since no bearings?
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Old 01-29-2013, 05:04 PM   #156
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[QUOTE=wfopete;20497151] I believe using a standard 490 piston is a common practice in 465 motor builds, which gets you purty close the Maico 490 B/S ratio.
QUOTE]

Hi Pete,

Is this true.

Back in the day I used to run a suzuki RM400 piston in my maico 400. The stroke was the same so the switch would give me 417cc (like the RM) in the Maico. The wrist pin diameter was the same but we had to mill the piston to fit the wider maico wrist pin bearing (if I remember correctly!).

There was a period of time when it was common for the ring locating pin to fall out of the mahle piston. The suzuki piston was reliable and much less expensive.

I have been weighing a variety of 465/490 pistons I have collected and will soon post the info I have collected thus far.
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Old 01-29-2013, 05:10 PM   #157
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Originally Posted by Frank121 View Post
Your bike looks awesome! Did you find any swingarm wear at the shock mount location?

I have a little free play at that location on mine and I'm looking for a way to fix it? Drill and sleeve, Weld and re-drill?
I haven't found a kit anywhere but there probably is not one since no bearings?

Thanks Frank!

There are bushings lightly pressed into the swing arm at the shock pivot. These are replacable although I dont recall if the parts are still available from Yamaha. Sometimes the pin can have a little wear also.

Not too long ago I bought some bronze bar stock from Enco. I am intending to make a bushing for the clutch cover kick start hole someday. You could use the same material to make bushings for the shock pivot.

Good luck with your bike.

Kevin
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Old 01-29-2013, 05:56 PM   #158
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Pistons

Over time I have collected a fair number of new and used 465 / 490 pistons of various oversizes.



Some are OEM Yamaha and some are Wiseco. Wossner also makes pistons for the 465/490 but I dont have any of these.

The Yamaha pistons are cast pistons while the Wiseco's are forged. The cast pistons expand less than forged pistons as they heat up. Yamaha specifies ~2.5 to 3.5 thou clearance in the various 465/490 manuals I have with the larger 490 piston at the upper end of that range.

The forged pistons are claimed to be stronger and lighter but require greater clearance or they will seize when hot. I
had trouble finding clearance specifications for the wiseco but I did find a application note from JE pistons that gave guidance on clearance for their forged pistons. The clearance they spec varies according to bore size and application but for a yz sized piston it seems to be around 4-5 thousands.

This seems to agree with what I see in my IT490 with 1.5mm wiseco piston. Knowing about the greater expansion rate of these pistons has made me more inclined to let the bike warm up before really cranking on it. I have not had any problems with mine but can understand how one might experience seizures if a wiseco was used with Yamaha OEM clearances.

With all these pistons around, I thought I would weigh them to see how much they varied across bore size and between vendors. I used an old triple beam balance that I calibrated against the weight of 10 pennies.



I measured each piston with rings, wrist pin and bearing (the wiseco rings are thinner than the OEM yamaha's).

Here is a table with results I have so far. Columns are listed for Yamaha, Wiseco and Wossner. Rows are for 0 through 8th oversize.

"Yes" means the listed oversize is available but I dont have one to weigh. Otherwise I list the weight in grams. Red indicates the oversize is not available for that particular vendor.

There is one case where I have a yamaha and wiseco piston in the same oversize (490, 2nd over). The wiseco piston kit is about 12 grams lighter than yamaha.






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Old 01-29-2013, 07:55 PM   #159
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Top end continued...

So as mentioned earlier in this thread, I wound up running a 1mm oversize YZ465 cylinder giving 476cc.





One thing to watch out for is the base gasket. The later version Yamaha (and some aftermarket gaskets) have a sealer as shown below. This is an improvement on earlier gaskets with no sealer.I became aware of this issue when my IT490 developed an air leak using one of the earlier gaskets.



The cylinder head was painted in silver enamel and baked in an oven.



And then the motor, with assembled top end, was bolted back into in the bike.



The stator plate was pretty dirty...





I used contact cleaner to clean the plate and various ground contacts. I also cleaned and checked the mounting screws and wiring harness. I did not go overboard on the coils as I did not want to stress the wiring or insulation.






After cleaning, the stator was mounted to the engine and the timing marks were aligned as specified in the manual.
Both crankshaft and flywheel tapers were carefully cleaned. A light grinding compound was then used to lap the tapers together to ensure a tight fit. The tapers were cleaned again and a new flywheel key was used when mounting the flywheel for the final time.








I could not find my flywheel holder tool so used the old tie down flywheel holder trick.

Using a tie down, hook one end to the frame then make a couple of wraps around the flywheel like this



Hook the other end of the strap and pull up tight.



Then use one hand to put weight on the strap to tighten and hold the flywheel from turning while you tighten the flywheel nut
with a torque wrench with the other hand.

Sorry, but with both hands occupied, I could not get a photo of this final step :-).





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FJ_Kevin screwed with this post 01-30-2013 at 07:53 AM Reason: Add missing pictures
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Old 01-29-2013, 09:09 PM   #160
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Helmets

My last motocross helmet was a nice Bell Moto 3. Unfortunately, the foam in the liner disintegrated over time. Thinking my mxing days were behind me, I threw the darn thing out sometime in the late '80's!

That was a great looking helmet and the one I buy today if I still could.

Most of the new helmets dont appeal to me because of the crazy graphics and odd color schemes. So instead of buying a new one, I picked up nearly new Bell Moto 5 that I have been using for the last 2 years. But even though it was in good shape, it is an old helmet and past its prime I am sure.

Then I found this reasonably priced ($107) HTC helmet with both DOT and SNELL 2010 approvals. I believe either AHRMA or AMA will require snell 2010 this year. I am not sure if they actually check this at the races but didnt want to have any problems.

The HTC iscomfortable and a good fit. The best part is that it is plain white. I was not wild about the visor so decided to mount a traditional Paulson Moto Peak visor in blue. The goal was improved safety with old school looks.

The Moto Peak visor is not a direct replacement. New snaps are required to make it all work. Here are the steps

Helmet with new fangled Gen Y visor,




Old school moto peak like I last used 30 years ago,



Note there are 3 - 6mm screw holes in the hjc helmet to hold the factory HJC visor but no provision for a standard type visor.

Therefore it is necessary to mount five snaps to the helmet. I found the snaps to be available from the Motorcycle Superstore (3 snaps per package).

The snaps come with screws to mount to the helmet. I placed the visor up to the helmet and marked the desired snap location with a pencil. Then I drilled a hole for the snap screw.



Four of the five screws are mounted in this way. However, the center snap had to screw into the snap location as the original 6mm scew.

The work around was to cut a short section of 6mm screw to use as a stud to fill the original 6mm hole. A small hole was drilled into this trimmed 6mm stud for the new visor snap screw. The trimmed 6mm stud was screwed into the helmet and then the snap was then screwed onto the stud.

I actually did the center snap first as I wanted to make sure it would work before drilling holes in my new helmet :-)



The next photo shows the helmet with all five snaps.

The visor is vertically slotted at the center snap and so accomodated the offset center snap position as dictated by the original 6mm hole while allowing me to have the visor angle I wanted.




Anyway, it all went pretty smoothly and gives me a new helmet that looks a little closer to something from 1980.

This photo show a comparison of the HJC, a Bell Moto 3 and a Bell Moto 5. And yes, I do have Bell stickers to go on the HJC




Now check out this guys helmet



And some more Moto 3's

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Old 01-30-2013, 10:06 AM   #161
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Kevin,

I just received my 2013 AHRMA Handbook. Under section 3.3 Technical Inspection sub section 3.3.2 it states that Snell M2010 helmet are required for ONLY road racing and dirt track. All MX, PVMX and Cross Country must meet Snell M2005 or equivalent standard.

So in those respects you are good to go. Unfortunately, you modified your helmet and in the same section it also states that ALL helmets will be closely inspected for ANY damage OR modifications to the shell and inner liner. Any damage or modifications (to include non-OEM visors) to the helmet found will be grounds for immediate denial or disqualification from any AHRMA event.



























...just kidding about that last part
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Old 01-30-2013, 02:15 PM   #162
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Quote:
Originally Posted by wfopete View Post

...just kidding about that last part
Haha, lucky for me I saw your last sentence first before reading the first part. Otherwise, with the way things go these days, I would have believed!

BTW, I had a good time at the York PA swap meet a couple of weeks ago. Seemed to be a good turn out with lots of parts and bikes up for sale. They had an auction for the first time too. I was too busy to watch much of that but it looked like fun and folks were bidding. There were bike for sale out in the parking lot too.

This Montesa looked pretty good,



Here are some Hondas out in the parking lot.








Some top notch show bikes were on display indoors,





This Elsinore was in the auction as were the bikes behind it.



My understanding was that all the following bikes, with number 46, were from the same family









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Old 01-31-2013, 10:54 AM   #163
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Carburetor

With the motor back together and back in the bike, attention was turned to the carburetor. The YZ/IT 465's and early 490's sported a 38mm Mikuni carburetor with left side idle adjustment screw. Later 490's came with a 40mm carb so be careful when comparing jetting across the model range.

It is important to note the side of the adjustment screw because replacement slides are available in left and right hand versions. If you choose to buy a replacement slide, say with different cut away,you will want to make sure you get the correct one for your carburetor.

It's alway good to get things cleaned up before starting a carb rebuild. Like others, I have been moving away from using harsh carburetors cleaners (when possible!) in favor of something safer.

I had good luck with Pine-Sol on some Goldwing carbs I rebuilt a couple of months ago and so that's what I chose to use here.

The following photo shows several carbs going into a tub I picked up from home depot. These tubs come with a handy top that helps keep unwanted items from falling into the solution while the carbs are soaking.

Using the top also keeps the smell from being over powering.

I used pine-sol at full strength and soaked 4 (added one more after photo) disassembled carbs for about 12-14 hours.



And here they are after soaking,



The carb in front had a bit of corrosion in the top of the float bowl area but it should still work OK.




Here is one that's easy to miss.

The bell of the Mikuni accepts an air correction jet (see hole at 12 o'clock position) for some applications. The IT490 uses a jet here but it is completely left out for the YZ465. Aways a good idea to check this if you dont know the bikes history.



I already has some baseline jetting combinations in mind from experiments on the IT490. Before going forward I had to see what parts I already had on hand.

The main jets are along the top with values of 350 through 460. The needle jets are in the center Q2, Q4, Q8. It looks like I had 2.0 and 3.0 slides on hand. Pilot jets are mostly in the 35 to 50 range with one flyer at 80.



More to come...



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Old 01-31-2013, 07:48 PM   #164
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Cool stuff man. Thanks for sharing!
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Old 02-01-2013, 03:49 AM   #165
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I've had problems with discoloration when using the Pin-Sol method however I found if I follow up with a little soda blasting things really start looking nice. SB is cheap, EZ but a bit messy. Also, due to the wear and tear over 30+ years of use I often opt out for a new carb with nice fresh jets/slides/needles. Kevin, you might want to get a 3.5 slide to play with at some time too. Another option is using a good proven carb (a good thing instead of dealing with a mystery carb). Remember these bikes were originally designed to run on Yamalube R @ 32:1 but Yamaha also recommended Shell Super M or Castrol R30 mixed @ 20:1. Oils have advanced 10 fold over the years and who still uses those ratios? These are a few pieces of the puzzle to consider when getting ready to jet/tune. Your approach to jetting/tuning the bike can vary but some guidelines when tuning the motor are:

GOOD, fresh high octane fuel and oil
Decide on what oil/fuel ratio to use (probably what you want to race with)
Plenty of time (you don't want to rush this process)
One change at a time (don't change the PJ & MJ at the same time)!
A logical sequence of test events (Don't jump back and forth between jetting and timing changes)
A good, safe test area that offers hard packed dirt and deep loam (helps load the motor)
Many, many new spark plugs
Paper/pencil

Doesn't hurt to have a knowledgeable friend help around to lend a hand & tell you how they see the bike running. I also like to have some compressed air handy to blow any dirt/dust off the carb before disassembly. A 2 stroke tuning book to helps you keep your mind straight during the process too. YZ 465/490s are known for problems in tuning so don't make it any harder on yourself than you have too. If you have all the pieces in place tuning the motor can be a lot of fun instead of a frustrating ordeal. Do what you can to make it fun.
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