Project 90 (Stock 89cc And Beyond)

[90GTVert]

Just wanted to let everyone know it'll probably be next week before you see any updates here. Normally I just put all the facts together in an update, but I'll give you some highlights of a very a long 2 days, just trying to install and tune the next exhaust...

Had to make a new bracket.

Snapped off a cheap bolt inside the cylinder when tightening the exhaust. Disassembled the engine to get the bolt out.

Had a soft seize with the 85 main in. Fired it up and it almost immediately seized again at 1/2 throttle where it is normally a bit rich. Got caught in a downpour with a scoot that I could barely give any gas on the way home.

After fooling around with odd results with different adjustments for the rest of that day, I opted to do a leakdown test today.

Found a leak at the base gasket. Disassembled again and fixed.

After more tuning attempts, I realized I'm going to have to buy pilot jets to get the stock carb working right. It would work OK with the needle lean and the mixture screw out a good bit before... when it was 50-60 and low humidity. Now it's 75-85 with very high humidity and with the larger jets it's gonna need, I can't compensate with the needle.

Pilots are $6 each and I've used a lot of spark plugs trying to get accurate reads since I've had so many weird results. Ordered 5 pilots that I hope are correct. Realized I was over on what I could cover on the credit card this month. Crap. Probably gonna try and get a few more spark plugs anyway. I have to tune so many times for this project, I'm gonna go through a truckload of them for the mods that require much dialing in. Imagine installing a part. Tuning for that part. Riding it once for 20-40 miles. Moving on to the next mod.

So yeah, it's been a frustrating 2 days. I think it gets me mad quick because I'm spending money on stock stuff I don't want anyway. I'll get it, it's not that complicated or anything, just gotta wait on the pilot jets. No way around it. I removed the snorkel and it did help, but then it seems like I need a much larger main to compensate. I'd like to get accurate numbers so I can give a rough upjet requirement that may be useful to folks doing this stuff, and I don't feel I can do it when I'm making mods to airflow along with the other mod. I've always had a drawer with tons of perfectly good plugs that have been used for chops, but it's growing fast. I'll have no shortage of plugs for scoots that are in tune already for sure though. lol

Sorry for the delay, but I assure you it's not for lack of effort.

[lshigham]

The stock Trition exhaust is the same as the one that came with my 139QMB. A little worrying.

That's some proper dedication to research :thumb:

[2strokd]

Im willing to throw in $10 toward the 89cc and beyond fund if you would like. Its not much but it will help with a few plugs or so. If a couple others could help too, we can keep this project moving.

[90GTVert]

I've got enough plugs to get by till I have more money, so it won't stop just yet. Hopefully I won't keep needing parts. It really doesn't help that I bought a 19mm Dellorto PHBG this morning for $50 shipped. Hard to pass that up and I didn't know I needed pilot jets at that point.

[2strokd]

Thats a good deal!

[lshigham]

What spark plug does it take Brent? I know of a site in the UK where they're more like $3.

[90GTVert]

I use BR8HS. I just said screw it and ordered a box of 20 on eBay for $48 shipped. That oughta last me a while. lol If I start out lean on a plug it's not bad. Then I can still use the plug over for reads. If I start out rich though, I have to get a fresh plug. I can get in range without ever checking, but sometimes a few jet sizes will feel fine and I like to look at the plug so I know if I'm getting enough fuel for sure. I used to use them over and over when I was reading plugs wrong. Now that I read them the proper way (I think, so many sites say this or that is the correct way, but I think I found the right one), I have to swap out plugs once the mix ring gets dark.

My spark plug drawer. I was wrong, all my new plugs are for GY6s. I do still have one plug that is white from a lean read I can use over though. I've given a bunch away when I used to work on scoots too. Anyone with a 2T that had a cheap plug or a nasty plug got one for free. I've thrown out a lot of the blackest ones, cause I'll just never use them all.

[lshigham]

That's quite a collection

Have you tried using a blowtorch to heat the insulator up to self cleaning temps? Or, you can actually clean up the ones that aren't too bad by running them in a correctly setup scooter to burn the deposits off.

[90GTVert]

I've never been able to clean the mix ring. I even tried throwing a dark plug in a scoot that was leaving plugs looking new once and it never cleaned it. Just came out looking very dry and sorta lightened it. I think I'd go through more cylinders than it would be worth by the time I cleaned a plug or two that way. lol Gimme a bit, and I'll write something up to show how I do it. I've been hesitant to do so, because I may still be wrong... but then so are some of the other folks that claim to be spark plug experts so I guess I'm no worse. At least I admit I don't know everything about spark plugs so anyone can use my advice with caution rather than assuming I have a clue what I'm doing. lol

[90GTVert]

It's not done yet, but you can get an idea of what I do here...

49ccscoot.proboards.com/index.cgi?action=display&board=gentech&thread=1727&page=1

[90GTVert]

I got the pilot jets in today. Didn't know what stock is, so I ordered 25-35. I had seen that Polaris 90s used a 32 stock somewhere, so I thought that should surely cover it. Nope. The 25 is bigger than whatever stock is. I put it in just to be sure and I can barely rev it up. Filled the garage with smoke very fast. :doh:

[lshigham]

25's too big! Even my lil 50 came with a 32 pilot

[90GTVert]

I ordered from 22.5 to 12.5. That makes $75 in pilot jets and $48 in spark plugs this week. :stars: T1's gonna get good and dusty waiting on ignition stuff at this rate.

[90GTVert]

This thing is being a real pleasure to work on.

I got the pilot jets from 22.5 to 12.5 in today. Looks like the stock pilot jet is a 22.5, which is also what Larry had mentioned. I'm not 100% sure, but by comparing them, it's definitely closest to that. Stock is on the bottom in the pic.



As you can see above they are a bit different from stock, but the closest I know of. If you know of the direct replacement, lemme know. Here's the difference installed.





Even with a tiny pilot, it's chugging and doesn't wanna rev. I went to the leanest needle position and down from 95 to 80 on main jet. Still pours out smoke and struggles to rev and run without the airbox off. I thought maybe the new jet fit was affecting it or something, so I tried modding one to be more similar.



No luck, so I pulled it all apart and thoroughly cleaned the carb with carb cleaner and air. Verified that the auto enricher is working.



Still no luck. Went back to the stock jet again. No luck. Did a leakdown test again, no leaks. I've had rich issues before from a busted CF reed, so I went there next to see if the stockers were sealing. It doesn't look like it should cause much trouble, but I pulled the reeds out and flipped 'em and bent em' a little to make 'em wanna seat more. Letting the crankcase air out to be sure that's not a problem too. Here's a pic showing a little daylight through the reeds before I messed with 'em.



If it'll start cooperating with me, I'll get you some useful updates soon I hope.

[90GTVert]

Reeds accomplished nothing. Still really rich with the airbox on, but revs nice with it off. Dies after a second of WOT being too lean though. Pulled the airbox apart to be sure nothing was out of whack in there. I guess I can keep moving down on jetting, but I don't know how it would go from needing an 85-90 to being so rich it can't rev on an 80. The float height has been fine, had the bowl off what feels like 1,000,000 times. I suppose I could try setting it lower than normal to see if that does anything.