Road Toad with a frog in its throat

[matt glascock]

Hi all, 1975 Model 99 Road Toad. Running stock oil injection. It was fouling plugs (B8HS and BR8HIX) right and left. Calibrated the oil injector and confirmed function. I thought maybe it was burning tranny oil due to a clutch-side blown seal resulting in air leak. The motor passed a leak down test. Timing is on. I Changed to a B7HS plug which seems to have solved the problem. Now, the bike blubbers in 1st and 2nd gear at about 50% WOT. Once I hit 3rd through 5th, the bike revs out like a champ. I'm running stock induction with stock jetting and have performed a complete carb disassembly and cleaning. For completion's sake, the entire bike is stock. What am I missing? As always, many thanks!

Best,

Matt

[viclioce]

Fuel type? 91 octane or better with no ethanol? Assuming all these are true.

Matt, what's your elevation? And what position is the clip on the needle? #3 or different? Is this something new just coming up? ; D Victor

[matt glascock]

Hi Victor, We are at a whopping 897 feet above sea level here in Cedar Falls, Iowa. Fresh, branded 92 octane straight pump gas without ethanol is what I'm running. I'm running a 2nd over fresh piston/cylinder combo with about 6 hours on it. Prior to changing to the hotter plug, I was having the fouling issues which have now resolved with the B7HS NGK plugs. I can't comment when this problem started as the bike was not running correctly prior to the plug change. Needle clip is in position 3 (stock). All stock jetting for that matter. As an aside, you should consider confirming oil pump function. The original piston/cylinder that came with the bike suffered a catastrophic seizure due to a malfunction in the oil pump. Since it was on its 6th (!) overbore, Hodaka Dave fixed me up with a sweet freshly bored jug/piston set. Now I check mine for function and calibration every 3-4 refuelings just to make sure it still operates. Takes a minute and saves a ton of heartbreak. I'd hate to see those fresh Toads of yours suffer the same fate.

[mac]

Hey Matt, do you think it could be an ignition problem?

Does it start okay when hot or cold?

I think in Maxies one day project thread there was an issue with a faulty choke plunger,maybe that?

Just throwing some ideas out there for the more experienced on here to chime in on.

[matt glascock]

Thanks Mac, I really went through the carb but your idea of extreme enrichening is valad. I did a few jetting runs up and down the street while, at the same time, thrilling the neighborhood and so far the plug reads are consistent with proper jetting. The thing that doesn't make sense is why it runs well in the 1/2 and above throttle range in third gear and above.

[taber hodaka]

Blubbering is a sign of a over rich carburetor. I would increase the main jet and drop the needle one notch at a time. -------Clarence I jet by sound not plug readings. And I would jet to a colder plug.

[viclioce]

Matt. My Toads are going premix. The pumps are there, but not in use. 28:1 for break in and 32:1 after. I'm stock as well. 160 main, #30 pilot and stock needle in 3rd position. Motor goes in the Red Toad tomorrow. Then the pipe& all the new cables. Still need fuel line and a T but that's easy stuff now! I may need to drop to a 150 or 140 main as I'm at 7,000 feet! Victor

[matt glascock]

Can't wait to see the finished scooter!

[viclioce]

Get it figured out yet Matt??? Victor

[matt glascock]

Negative, but reverses in weather cooperation have put the brakes on further testing and tuning. Today has prospects, though.

[Bullfrog]

I guess I would like to confirm a couple of things.
1) What is the confidence factor that the burbling (richness) is happening at half throttle? Inadvertantly holding 1/4 or 3/8 throttle while going through the lower gears would be pretty easy to do just to keep revs from rising too quickly to get a "feel" for things.
2) Are the jetting tests being done on an uphill to assure there is a good "load" on the engine?

These questions are being asked because being rich (or lean) is a throttle position thing . . . and not so much a "what gear it is in" or "what is the engine speed" thing. So good repeatability of throttle position and discernment of throttle position is really important. And being on an uphill helps stretch out the time in any given gear as the machine accelerates . . . which provides the on-board "Doctor" time to diagnose the situation. In addition, the uphill assures a good load on the engine even in the lower gears.
Ed

[matt glascock]

Thank you Captain. I need to do a little homework so you'll have more specific data to process. Right up front, I see I was not clear in my description of the situation. The jetting runs were performed on level pavement, so I'll fix that. The half throttle description was really "halfish" so I will make a throttle scale so that I can provide a more accurate assessment of at which throttle position the motor bogs in 1st and 2nd. As it sits, in first and second gear, blubbering begins at the "one-halfish" WOT point and and the engine won't rev any higher beyond that throttle position. Once in third and through 4th and 5th, the motor will rev to the moon. For the jetting runs, while in fourth gear, I buttoned the engine at WOT after about a 400 yard run at speed (level pavement). The plug reads proper jetting with a light tan/brown tint on the insulator nose. Also, I must confess my tendency of hammering on the throttle (bad motocross habit, but what the hell - the Super Rat loves it). I will redo my assessments more precisely and report. Many thanks, Captain!

[Bullfrog]

To nail down carb jetting . . . ears are better than eyes on spark plug (per Clarence's comment). Spark plug readings are wayeeee more useful to discern internal conditions in a somewhat steady state, long term (10's of seconds) situation - and confirm that all things are correct. Timing, compression, jetting, fuel quality, plug heat range, etc. If only one of those things are wrong . . . the plug reading can be scary . . . and it can tax a truly experienced two-stroke tuner to figure out which one (or more) of the items are wrong.

Is the O-ring on the bottom end of the main nozzle in good shape?

Ed

[matt glascock]

Aye Captain. A new O-ring was installed when I overhauled the carbureator. Very tight fit when reassembled requiring grease to replace. Maybe I've displaced or tore the o ring. That would be sweet. Now I must confess my negligence - I totally missed (!) Clarence's comment. I'm such a moron. My apology, Clarence. I was having endless fouling issues with the one-step colder plug (NGK B8HS). I know its a rookie move to try and solve carbureation problems with a hotter plug, but at least I confirmed an air-tight motor before I resorted to the B7HS plug. I'm going to dig back into the carb and check that o ring and then get on with some calibrated runs if all's well. Thanks fellas!

Best,

Matt

[taber hodaka]

Matt we went from a engine that blubbered in first and second now to an engine that bogs in first and second big big difference. Ed has you covered. When you get her running on the bottom and keeping your top end you will have a screamer. I will watch with great interest. Harry was the best tuner I have ever known and Ed was there to see and hear it happen. Matt it is so good to see you and others like you moving the ball forward------Clarence

[michael_perrett]

Where is the O ring in this type of Toad carb?

Mike Perrett

[viclioce]

Matt. Are you referring to the O ring on the choke plunger, #26 in the parts diagram, or is there another rubber O ring somewhere? The float valve gasket in mine is either cork or some kind of synthetic which looks similar to cork. So I'm guessing it wasn't that one to which you're referring? Let me know! Victor

[Bullfrog]

Uh-oh. Mike is right - the stock model 99 carb doesn't have an O-ring at the bottom end of the main nozzle. The main jet threads into the main nozzle (needle jet) with a custom washer/fuel splash controller plate.

So the carb Matt has isn't stock on the 99 Toad since it does have an O-ring on the bottom of the needle jet. Hmmm . . . .
Ed

[viclioce]

Hmmmm. Answers my question too! Victor

[matt glascock]

AHA!!! Non-original carb! Very clever question Mike. Seems as though you smelled a rat too, Victor. Then Ed set the record straight. Great work, fellas! I should've been more astute. This bike was a train wreck when I acquired it several years ago and it is my one and only Toad so I didn't have the experience to pick that up. That's really a testament to how adaptable and serviceable Hodaka motorcycles are. Some DPO must've slapped that carburetor on there years ago to keep the bike in service. The bike hadn't run in 25 years before I bought it. It must have the same throat as the stock air box and boot fit. Good news is I picked up a spare model 99 Toad carburetor in a parts stash I scored a few years ago. It will need a rebuild but it is black, which I understand to be stock, and the one on my bike is bare metal. And my apologies for using inaccurate terminology, Clarence. Its a blubberer and not a bogger. I'll rebuild and install the proper carb and report. Hopefully this weekend if I can convince my wife to fly solo with the ten (yes 10!) little girls invited to my daughters 10th birthday sleepover. Hmm...not likely. That would probably result in the invention of a brand new party game - pin the baseball bat on daddy Many thanks, gentlemen!!

[viclioce]

Pics of the carb when you get it off Matt! Like to know what else was put on that Toad! It is still reed valved, right? Victor

[matt glascock]

Will do, Victor. Yes, I'm still running reed valve induction.

[viclioce]

So it's not a flange mount carb then. Cool. Would like to see what carb was used. I'm assuming it's still a Mikuni?

[matt glascock]

Yes, it says MIC and it is spigot, not flange mounted. I had a good friend and riding buddy over (he's functionally encyclopedic in his knowledge of "big four" dirt bikes of the 70's) who opined its origin was likely mid- to late 70's Suzuki RM 100 upgrade to the stock Keihin units. I, of course, stood there and offered informed quips such as 'sure' and 'that makes sense to me'.

[viclioce]

Sure! That makes sense to me! LOL!!!